Thanks. I have done that successfully. I also did this that I found here at the bottom: UMC "Internal server error"
apt-get install --reinstall $( dpkg -l 'univention-management-console*'|awk '/^i/ { print $2 }' )
Then I rebooted everything in my site (modem, wifi’s, switches, VMs, and UCS). It all started working normally again.