I'm connected from my Windows 7 machine to my Ubuntu machine (18.04 LTS). What's happening on the Ubuntu screen doesn't show up on the TeamViewer session after getting connected. I can see the initial desktop, but if I do something such as open a browser or look at settings, the window opens on the Ubuntu desktop, but it doesn't show me that on the remote session.
The behaviour observed by Grodech is happening to me as well. Sometimes TeamViewer works but sometimes the screen shown to the client does not reflect what is happening on the host screen. Its like the screen is frozen when TeamViewer connects.
I tried 13 and 14 on 18.04 (minimal install) and no joy. Went through all community posts. Tried everything and neither would connect to the Teamviewer server. Even tried wine. Finally loaded the Windows version in a virtual machine.