Enter Postgres Hyperscaler Edition from Cloud Integration (CPI/HCI)

I opened a trial account and enabled CI and a Postgres Database.

Now I want to access the postgres from CI. I added JDBC Adapter with credentials from key file and a jdbc connection string like:
jdbc: postgresql://postgres-xxxxxfxx-85bf-4909-9476-b579cdc8893d.ce4jcviyvogb.eu-central-1.rds.amazonaws.com :4638/cMXXXXxxxZQ?ssl=false&loglevel=2

Unfortunately i always get org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is org.postgresql.util.PSQLException: Connection to postgres-xxxxxxx-85bf-4909-9476-b579cdc8893d.ce4jcviyvogb.eu-central-1.rds.amazonaws.com :4638 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections., cause: java.net.ConnectException: error 111 - Connection refused (Connection refused) (local port 55746 to address 10.145.79.214 (33c72b56-d8a4-417f-7cd5-1ffc), remote port 4638 to address 10.16.56.221 (ip-10-16-56-221.eu-central-1.compute.internal))

Can anyone help here? do I need to establish a special connection between CPI and Postgres?

BR and thanks for the help