Attempting to activate a DAG mailbox database in Exchange Server 2019 EAC fails with the error: …”Server ‘exchangeServer.contoso.com’ is not up according to the Windows Failover Cluster service.”

Problem

You attempt to use the Exchange Admin Center (EAC) to activate a mailbox database in a DAG cluster but noticed that one of the nodes fails with the error:

Mailbox G to L
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:

         exchdr01:
         Server ‘exchdr01.contoso.com’ is not up according to the Windows Failover Cluster service.
          [Database: Mailbox G to L, Server: exchprod01.contoso.com]

You log onto the server exhibiting this problem and notice that the services console indicate the Cluster Service is Disabled and not started.

Solution

This error through me off for a bit of time as the node was added to the cluster for a few days and the process did not throw any errors.  It was not until I decided to make modifications to the DAG configuration when I received the following error message that made me realize the node wasn’t added to the DAG properly:

[PS] C:>Set-DatabaseAvailabilityGroup -Identity DAG15 -DatacenterActivationMode DagOnly

The following servers have been added to the database availability group but not to the cluster: drexch01. This is
usually the result of an error during membership change. Removing and re-adding the servers can correct the issue.
     + CategoryInfo          : InvalidArgument: (:) [Set-DatabaseAvailabilityGroup], DagTaskServersInAdNotInCluster
     + FullyQualifiedErrorId : [Server=exchprod01,RequestId=f9520afa-3fce-4cd2-9e22-648339c8eca5,TimeStamp=3/17/2019 8:05
    :23 PM] [FailureCategory=Cmdlet-DagTaskServersInAdNotInCluster] 86538C81,Microsoft.Exchange.Management.SystemConfi
   gurationTasks.SetDatabaseAvailabilityGroup
     + PSComputerName        : exchprod01.contoso.com

[PS] C:>

Simply removing the mailbox database copies on the problematic node, remove the node from the DAG and re-adding it corrected the problem of the cluster service as well as database activation.