Oracle Data Guard 19c TNS-12564: TNS:connection refused

 I faced this error during the switchover in 19c version:

Make sure:

1- Have the correct services statically registered.

2- Configure the local_listener as below in both primary and standby servers:

alter system set local_listener='(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=primary)(PORT=1521)))' scope=both;

alter system set local_listener='(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=standby)(PORT=1521)))' scope=both;