By using a Oracle database as Q-DAS configuration-database, the error message "Database check failed" appears when trying to log in.
The reason for this is an unsupported / too old Oracle client.
Here, for example, an Oracle client 12.2.0.1.0
Please note that especially with Oracle databases, only some combinations of server and client version are tested and supported.
Oracle server versions 21c and 19c as well as Oracle client versions 21c and 19c.
Any other combination is not supported.