Assume that you use Read-Scale Availability Group (AG), for example "CLUSTER_TYPE = NONE" in SQL Server 2017. If you stop the primary replica and fail over a synchronous mode secondary replica to primary, synchronization will be failed. Additionally, you will receive Not Synchronizing message from new primary AG database.
Note: This issue does not occur in SQL Server 2017 RTM.
This issue is fixed in the following cumulative update for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminologythat Microsoft uses to describe software updates.