"An error has occured" when clicking on report (On Prem)

Halle everyone,

for some weeks now everytime i click on a report on our reportserver i get this:

There is no more text to the error. And the only thing im doing is clicking on the report.

i tried updating to the latest version (version: 15.0.1111.115) but it didnt help.

With PowerBI Desktop (January 2023) i cannot open nor save PBI Files on the Server. Same issue:

Thank you in advance for any advice.

KR Gordan