An interesting issue occurred in a client environment today. The configuration was an Always On Availability Group which had a primary replica(Also a SQL cluster), a reporting replica(non-voting) and a DR replica in a different data center. There was a cluster issue the previous night which saw the report server removed from the cluster. The cluster and the availability group both recovered within 60 seconds. However one of the databases in the AOAG could not be queried from. The Availability group confirmed the database was healthy and data was transferring to it fine, but any select query just ran forever.