No authentication key files error

[eseper]

Hello
After reinstalling the master PC, I reinstalled Veyon and set the same key as before, however I can't get into Veyon Master because of this message:

No authentication key files were found or your current ones are outdated. Please create new key files using the Veyon Configurator. Alternatively set up logon authentication using the Veyon Configurator. Otherwise you won't be able to access computers using Veyon.

This is when key-file authentication. I tried with a new key, but the message is the same. Windows 10. Please help.