DAG Node lost access to File Witness Share

Today on my own companies network 4Logic IT Solutions we had an issue when trying to activate a database copy inside a database availability group (DAG) cluster.

When attempting to move the active mailbox database to another node using Exchange Management Console (EMC) or Exchange Management Shell (EMS) the following error was experianced.

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Microsoft Exchange Error
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Cannot activate database copy 'Activate Database Copy...'.

Activate Database Copy...
Failed
Error:
An Active Manager operation failed. Error The database action failed. Error: An error occurred while trying to validate the specified database copy for possible activation. Error: Server 'QV1-EXC1.4logic.lan' is not up according to the Windows Failover Cluster service.. [Database: QV1-EXC1-Database-01, Server: OP-SRV1.4logic.lan]

An Active Manager operation failed. Error An error occurred while trying to validate the specified database copy for possible activation. Error: Server 'QV1-EXC1.4logic.lan' is not up according to the Windows Failover Cluster service.



The error stated that Windows cluster services reported the node as being down. So I fired up Failover Cluster Management MMC snapin to investigate further. The following errors were being generated:

File share witness resource 'File Share Witness (\\qv1-utl1.4logic.lan\DAG01.4logic.lan)' failed to arbitrate for the file share '\\qv1-utl1.4logic.lan\DAG01.4logic.lan'. Please ensure that file share '\\qv1-utl1.4logic.lan\DAG01.4logic.lan' exists and is accessible by the cluster.



Node 'QV1-EXC1' failed to form a cluster. This was because the witness was not accessible. Please ensure that the witness resource is online and available.



I went over to my server hosting the File Witness Share QV1-UTL1.4logic.lan. DAG01$ was the only trusted object added to the Share permissions. I added Exchange Trusted Subsystem and my Administrator account (for testing purposes) to the Share Permissions.



I then restarted the Cluster Services service on QV1-EXC1. After the permission change the cluster service came online again.