If you have an even number of Exchange Servers is a DAG, then you MUST have a Witness Server, otherwise the DAG is not configured correctly.
I would:
Run these commands:
test-replicationhealth
get-mailboxdatabasecopystatus
If those look good.
Dismount the databases
Shut the Servers off.
Then once , done
Restart all the servers and File Share Witness
Wait a few minutes.
Check the event logs on the Exchange Servers for anything unusual
Run those powershell commands again:
test-replicationhealth
The mount the databases.
Wait a few minutes:
Run again:
test-replicationhealth
get-mailboxdatabasecopystatus