Cannot backup all hard drives in Windows: Cannot get volume for path "F:\"

Error: Cannot get volume for path "F:".

Urbackup server: linux
Urbackup client: Windows 2019 Server

My Windows 2019 has 3 volumnes: C:, E:, F:
I was backing up only C: and E:, no problem.
Since recently I added F:, I always get this error.

Thanks in advance

What method did you use to ADD the ‘F’ drive to the list of drives to be backed up?
Web interface?
Tray Icon on WIndows?
Hand edit client file?

Also - did you reboot the Client and the Server? (Should not be necassary but – maybe helps)
David