Hi
Unfortunately, nightly packages crept into the Debian "main" repositories after the build tool changes on 15 Oct 2016.
The Debian repository has been taken offline for the time being pending investigation.
If you have installed or updated X2Go "main" packages for Debian from our repository on 15 Oct 2016 or later, you will have to proactively remove and re-install all X2Go packages once the repository is available again. I will reply to this thread once the situation has been rectified.
Best regards,
Mihai