Hi Nowak, Wawrzyniec •,
Welcome to Microsoft Q&A forum.
As I understand, you Cannot connect on 6432 while promoting read replica in Azure Database for PostgreSQL Flexible server.
Could you please try reloading pgbouncer and check if that works?
The Promote to primary server action is currently in preview. The Promote to independent server and remove from replication action is backward compatible with the previous promote functionality.
Awaiting your reply, thanks.