Timescaledb cannot connect

Hi,
I want to use timescaledb as a replacement for influxdb and rrd4j.

Environment: Kubernetes with OH4M2

I am using the jdbc extension for this.
When I use jdbc:timescaledb… i am getting a lot of errors like this

2023-06-03 23:00:48.380 [INFO ] [persistence.jdbc.internal.JdbcMapper] - JDBC::openConnection: Driver is available::Yank setupDataSource
2023-06-03 23:00:48.381 [WARN ] [persistence.jdbc.internal.JdbcMapper] - JDBC::openConnection: failed to open connection: Failed to initialize pool: The connection attempt failed.
2023-06-03 23:00:48.381 [INFO ] [persistence.jdbc.internal.JdbcMapper] - JDBC::openConnection: Driver is available::Yank setupDataSource
2023-06-03 23:00:48.381 [WARN ] [persistence.jdbc.internal.JdbcMapper] - JDBC::openConnection: failed to open connection: Failed to initialize pool: The connection attempt failed.
2023-06-03 23:00:48.381 [WARN ] [jdbc.internal.JdbcPersistenceService] - JDBC::store: No connection to database. Cannot persist state '15.3' for item 'WGT_Temperature_Outdoor (Type=NumberItem, State=15.3, Label=Temperatur Außen, Category=null, Tags=[Temperature], Groups=[Temperature_Outside, E_WGT_Technik])'! Will retry connecting to database when error count:0 equals errReconnectThreshold:0

When i use jdbc:postgresql… its working fine (but without the timescaledb extension inside)

What am i doing wrong?