I improved the error message to understand the reason. Now we get the following error message:
ConnectionError: Database (oep) connection not successful.
URL: http://oep.iks.cs.ovgu.de//api/v0/schema/supply/tables/wind_turbine_library/rows/?
Response: [400]
{"reason": "Connection limit for anonymous users is exceeded. Please login to get your own connection pool."}
How shall we deal with it?