Cannot add VM to Cluster

We have have Hyper-V 2012 Cluster with 2 Nodes that runs about 10 VMs, mostly Server 2008 R2 with a few 2012. Cluster storage is and iSCSI SAN with DSS7 from Open-e.

I have a VM that I cannot add to the Cluster.  Its Server 2012 that runs Exchange 2013 with about 50 mailboxes.   When I go to the Failover Cluster Manager the VM does not show up.  I have had no problems adding any other VMs. 

I am trying to determine why I cannot add this VM to the Cluster.

Thanks,

Todd