[ceph-users] dashboard object gateway not working

We are running Ceph 14.2.12 and would like to manage our object gateways via the dashboard. The rados gateways are running on different (virtual) machines than the mon servers (where mon, mgr and mds are running). The dashboard seems to be running fine. But when we cklick on "Object Gateway" we get the following error message : Sorry, we could not find what you were looking for 500 - Internal Server Error The server encountered an unexpected condition which prevented it from fulfilling the request. 10/27/20 12:30:32 PM The logfiles (of mgr and radosgw) do not show anything helpful. Maybe we have missed someting that needs to be enabled/installed/activated ?!? Any Ideas ?