Availability Database Join State
Secondary database is not joined.
This policy checks the join state of the database replica. The policy is in an unhealthy state when the dataset replica is not joined. The policy is otherwise in a healthy state.
This secondary database is not joined to the availability group. The configuration of this secondary database is incomplete.
Use Transact-SQL, PowerShell, or SQL Server Management Studio to join the secondary replica to the availability group. For more information about joining secondary replicas to availability groups, see Joining a Secondary Replica to an Availability Group (SQL Server).