Synchronous Replicas Data Synchronization State
Some synchronous replicas are not synchronized.
This policy rolls up the data synchronization state of all availability replicas and checks for any availability replicas that are not in the expected synchronization state. The policy is in an unhealthy state when any asynchronous replica is not in a SYNCHRONIZING
state and any synchronous replica is not in a SYNCHRONIZED state. The policy state is otherwise healthy.
In this availability group, at least one synchronous replica is not currently synchronized. The replica synchronization state could be either SYNCHONIZING or NOT SYNCHRONIZING.
Use the availability replica policy state to find the availability replica with the incorrect synchronization state, and then resolve the issue at the availability replica.
Resume the secondary database by using the following ALTER DATABASE statement:
ALTER DATABASE database_name SET HADR RESUME