Please try to check if details inside your app are correctly given.
Check permissions and network aspects too.
Try to enable detailed logging for the PostgreSQL server to capture more information about the connection attempts and reasons for rejection.
It is recommended to create support case for understanding your scenario and set-up since it involves multiple services and and in case if you don't have a support plan, do let us know here so that we can check on other options to unblock you.
Thanks