DAG in 'Disconnected and Resunchronizing' state

[disturbedone]

I have 2x mailbox servers in a DAG with about 12 databases. The backups via CommVault were hanging because the VSS writer was hung and the server needed to be restarted to resolve it. Upon restart one database has not come back correctly.

11 of the databases are working perfectly and are mounted on MBX2 and healthy on MBX1. But the main database (all users were originally in this but are being moved to others before decommissioning) has conflicting information - in the top panel it says it's 'Mounted on MBX2' but in the bottom panel (Database Copies) it shows MBX2 as 'Mounting' and MBX1 as 'Disconnected and Resynchronizing'. Mailboxes left in this database cannot be accessed. Against MBX1 the copy queue length is 0 and the replay queue length is 19.

How can this be resolved?

 

[disturbedone]

In this instance it sorted itself out. I left it in this state about midnight and when I checked again at 6am all was ok. A user has reported that they have emails arriving at 3am so it must've been fixed by then.

I'd still be curious as to why this happened and if there's a better way to resolve it that leaving it to sort itself out!