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When you see a pop-up offering you to Update Now, please check the version of the TeamViewer (Classic) software you are currently using, and immediately update to the latest version of TeamViewer.
This article applies to all TeamViewer (Classic) users who have not upgraded the TeamViewer (Classic) software to the latest version and see the error message: "Unable to connect - Reason unknown".
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At the same time, please check the compatibility of operating systems and software versions: Supported operating systems.
Solution
When you see the error messages in TeamViewer (Classic) with Reason Unknown, and the connection cannot be established, please download and update TeamViewer to the latest version.
Windows, Linux and macOS
When the TeamViewer (Classic) software pops up with an error: Unable to connect - Reason unknown, please update TeamViewer to the latest available version.
I am using Teamviewer 12 on Ubuntu 16.04 , while connecting to some of the host machines running same version of Teamviewer , I get "A connection could not be established. Reason unknown" error.
This is shown even after many a attempts and when both the machines i.e. host machine and mine have been restarted.
Am trying to connect away (laptop) with home/office PC. Every time i am away, i encounter this problem message. i need to get someone to click on the teamviewer icon on my home office computer to connect. I have enabled remote access, listed both computers as trusted "contacts" etc. Have updated to Teamviewer 12 on PC and laptop and still have same problem. please help.
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Comments
- Options Do you have set up unattended access? This is needed to connect with your own, always the same password and it sets TeamViewer to run at system startup. Connection -> setup unattended access will guide you to set it up. And follow this to make your host secure. »We are all born unique, but most of us will die as a copy.« 6
- Options TV will be working. Then when I re-estblish connection, it replies that TV is not running on Partner 2
- Options This is exactly what I get too. It works and then if I close the window on my home computer it thanks me for using it but I cannot reconnect later as it says it is not running on partner computer. 1
- Options I have this problem as well. It used to work just fine, and then suddenly something changed and I can't connect. I have rechecked settings multiple times. I tested the connection while sitting in front of the computer to confirm it was working, then tried to access it away from the computer and it claimed it was not running anymore. Now I'm wondering if it has something to do with the computer sleep settings which are preventing access after a period of time, though I can't think of any settings that were changed between then and now... 6
- Options same problem here. TV has always worked, have not touched remote computer settings and now 6 hour drive from remote offline computers on Christmas holiday. Unhappy. 2
- Options Been working on my machine remotely for a week. Nothing changed. Now I get this message and cannot connect to my machine. 2
- Options I have this problem as well. I have rechecked settings multiple times. I tested the connection with my partner's computer to confirm it was working, then tried to access it away from the computer and it claimed it was not running anymore. My partner is able to connect to my PC via TV, howerver I'm not able to connect to his PC via TV. Very frustrating. 5
- Options I setup TV13 on my desktop and I get this message anytime the computer sleeps. Anyway to connect when the computer is asleep without changing the sleep setting to 'Never'? 2
- Options HAS ANYONE FOUND A SOLUTION TO THIS PROBLEM?!! 8
- Options Exactly the same for me too. It was fine before. Something has changed. Perhaps they changed something in the latest update? I think there is something in the sleep settings theory as on one of the occassions I tried to connect to my desktop computer from my laptop, after failing, while I was doing something else, it notified me that my desktop computer had just come online. I think it's because I have a scheduled task that runs every hour on my desktop and, if I catch it during this time, I can connect. Frustrating but then I don't use it often, thankfully. 1
- Options The silence is deafening. .. I have the same problem, yes, configured to be in unattended access (which didn't work until I found and applied 'the fix'.... Yes, I don't use it that often but...it seems when I *really* need it, it doesn't work....sigh Suggestions? solutions? anyone??? 3
- Options I cannot believe there has been no attention to this issue. It is not a new problem either. There are bouts of unusability with software which steer me further and further away from it. Advice on alternatives that dont drop when you need it most? This is just costing me time & money, as im sure it is alot of other teamviewer users. 5
- Options after taking LOTS of time to find out and try some solutions on my own, I decided to look for alternatives to TV. I was surprised to find at least 6 that are free for personal use, and a few that have reasonable costs commercial (non-personal) use. Rather than beat my head against the wall trying to determine a fix, I'll try one or two of the alternatives. What really drove me to do this is the fact that my searches turned up LOTS of this type of problem that has been going on for over a year, with the same dead end...no solution proposed or discussed by Team view. That lead me to the conclusion that they just plain don't give a s**t.... 8
- Options What the **bleep** is wrong with TeamViewer? They are constantly advertising about buying their paid product however something like this goes unanswered for OVER A **bleep** YEAR!!! What I have noticed every time that I run into this problem is that TV shows the machine in question has been offline for so many days....even when I am on that machine and see the services running! I have used TV for several years, pretty much since it came out, and because of the lack of support I am jumping ship this weekend! 4
- Options I don't believe the answer is another program. I am experiencing the same problem on only one computer. I have tried other programs wth the same result. I believe that the problem is associated with the Win 10 sign-in screen. My other computers don't have this feature. It appears to me that the sign-in screen disconnects the computer from everything (probably as an energy saving measure). I say this because when I turn off the sign-in screen (by entering the password) I get a message that my scanner is ready to work. In fact, the scanner does nothing if the sign-in screeen is on. I tried to eliminate this sign-in screen, without success so far. After reading some of the comments I have jus now turned off all screen saving features. Perhaps this will work. Like all of you, I am disappointed that TV has not remarked about this problem. 3
- Options Alright everyone after a painful week of messing around changing settings testing changing them back and trying something else. I have found the solution. The problem in Windows 10 is related to the way in which the machine acts when you choose to sighn in with your Microsoft account credentials. I’m not sure why the lock screen functions differently but when you have Microsoft account sign in turned on the lock screen says CTRL-ALT-DEL to log in. So today i switched from using my Microsoft account to unlock the machine to using a local account and now I can use my TeamViewer account to wake and connect to the machine. Try it for your self. 2
- Options Really glad you've found a solution for Windows users. Us Mac peeps are still stuck in the mud... Bleh 0
- Options Everytime I've encountered this (including 30 seconds ago) it's been fixable by stopping and restarting the Teamviewer service. I only use Win7, but the process is start > run > TYPE "services.msc" ENTER Then find the TV instance on the right side, right click, stop, right click, start. Fingers crossed it keeps working. Also, typically it's a problem on the PC I'm using, not the remote machine (thankfully!) Good luck all. 0
- Options I have installed Team Viewer 13 on my office computer Linux Cent OS 7. I connect from my home Windows 10 computer. I am able to connect to other Windows machines from home but the Linux Cent OS 7 workstation. The latter apparently refuses connection after one hour (or two). It is like, you are able to establish connection for a short time. Then, the connection severs and I get a message "Team Viewer not running on partner computer", although it is running. Surprisingly, after this severing happens, if someone touches just the mouse on my office computer, the TV can reconnect. So the following are the possibilities- 1. Does Team Viewer sleep after one hour of connection at my office? 2. Is it because the office is behind a firewall? The problems keeps me going to office even on weekends, which is not great. 0
- Options I have this problem now to! Before all I had to do to ensure the remote machine connected was select "Accept" instead of "Accept Exclusively" in the "General" area under "Extras". However, that is not working either I still get an ip address showing instead of the id regardless of which option I select and apply. 0
- Options I had a similar problem with one of my co-workers. It didn't work either, but later found out that due to hibernation on win10 TV stops working, even though the computer is ON. Another co-worker also had the same problem but on this occasion i had to go into Task manager and kill all proccess related to TV, then start up TV and it worked after that. Dunno if this will help anyone. 0
- Options
- Options I agree. Every time window 7 updates and restarts my office computer I lose my remote connection from my home laptop. I have no idea why Teamviewre shuts down after an update. Has anybody else had this particular problem? 0
- Options I was having this problem as well. Then I got to thinking about when I used to use the free **Third Party Product** app. I don't remember which OS I had at the time, but was pretty sure it didn't have a "sleep" option (or else I had it turned off). So, I turned off the sleep option - can still log off - and have had an entire week problem free! If you're not familiar with how to do this, it will be something like this (may vary slightly depending on your OS version). On the remote computer access: Control Panel/ Power Options/Change When The Computer Sleeps and choose "Never". You can still time out the display to show your screen saver. Hope this helps ya'll! 0
- Options This worked for me: If we have two machines, the one we are connecting TO and the one we are connecting FROM. I exited TV and restaretd it on the machine I am connecting FROM and that worked - I could then connect to the other "TO" machine. Before trying that I had rebooted, etc. the machine being connected TO and that never worked. 0
- Options I'm having the same problem connecting from a Win 7 machine to a Win 10 machine. Restarting the teamviewer service does not work. I doubt it is related to the Win 10 sign on screen, as TV works for often two or three days at a time. Eventually though, I am unable to connect from the Win 7 machine and have to restart the Win 10 machine (which is headless, and a royal pain in my arse). 1
- Options I did, but still the same problem 1
- Options You just may have answered my question... 0
- Options I have three computers: one in my office, one in the lab and the third at home. My office computer gets this same message when I try to connect to either the lab or home computer. However, the lab and home computers connect just fine to both of the others! Why????????????????? Very frustrating. 0
JeanK Posts: 6,995 Community Manager 🌍
Options
Hello MEShields,
Thank you for your message.
In that case, if you are on a Windows operating system, I recommend you to restart the TeamViewer service.
-Execute "run", type "services.msc" and press OK
-Now find TeamViewer, and restart it by doing a right click.
Then, restart the TeamViewer application. It should work again.
If you are using iOS, I recommend you to uninstall TeamViewer with deleting the settings, and re-install it from our website here.