When subscriber (configured as Designated Standby) went out of sync, you may have noticed that Publisher marks the node as disabled / cluster sync status is disabled.
In such a situation, please use the below steps:
1. On a subscriber node (configured as Designated Standby), if needed take a logdb backup.
2. Perform a "cluster reset-database" (easily done in CLI)
3. Perform “Make-Subscriber” operation to join back into cluster (using either UI / CLI).
4. After the node is joined as subscriber, check if VIP Service is running on the new subscriber. If stopped, please start the same.
5. This will succeed and High Availability features like VIP and Publisher Standby configurations are restored on this Subscriber node.
Note: In the above steps, you need not drop any of the high availability features before joining the out of sync/disabled Designated standby into cluster. This way, time spent in getting back the out of sync subscriber node (or designated standby) back in action, is much lesser.