The remote TeamViewer is running an old version which is out of date
Turns out to be the TV license. My colleague had a working license in his viewer while my teamviewer was in "free" mode.
So the error is misleading. It should have read "you are trying to connect with the wrong license mode" instead.
After keying in our license in the
teamviewer.ini file it would connect just fine.
If you are using the "free" mode of Teamviewer for personal use and can't switch to a licensed version, both Teamviewer instances need to be version 14.