File Audit: No Data Available

File Audit: No Data Available

I have a problem with File Audit.
Nothing is displayed in the reports: (No Data Available)
All file\folder actions are logged on the server in the Eventlog Security from Server. 
auditpol /get /category:* shows correct result (compared with Help-Page)
Under "Configured Servers -> Windows File Servers" the status is "Success" and also under "Configured Shares" is all green.
"Eventlog Property" from this Server also shows me correct values.
The service account of ADAudit has full access rights to server and shares.
I've worked through the troubleshooting instructions several times, but I can't find any errors.

Targetserver: Windows Server 2019 core

Does anyone have any idea what the problem is?
Regards,
Coyo