When trying to use the mouse there is no right mouse menu. This happens when trying to create a new migration session or when trying to look up the synchronization properties.
Using the task bar one can still look up the synchronization properties, but no migration sessions can be created within right mouse menu.
Restarting, reinstalling QMM or performing a repair doesn't help.
Usually this is caused by different users accessing the console when using a terminal session.
Most of the GUI settings are user specific and are stored in the users profile.
It is not allowed to use the same console by different users simultaneously or to open multiple RDP (Terminal Sessions) when using the same account.
To resolve the issue log in as another user and confirm the right mouse menu works.
Then delete the old users NT profile and log in using the service account again.
Trying to use another account and another profile is helpful when troubleshooting any GUI abnormalities, eg. task bar disappeared, etc.