The cluster probe will report Cluster Groups on Windows 2012, particularly the 'Available Storage' group, as unavailable even when they are up and running.
Cluster probe: 3.31
This issue is caused by the cluster.exe command line feature not being installed and enabled by default on Windows 2012 machines.
The Windows 2008 has the 'cluster.exe' file in the windows\system32 directory while Windows 2012 does not have it present.
The Cluster probe requires this command line feature to work properly.
Using the above link as a guide, install the 'Failover Cluster Command Interface - RSAT-Clusterind-CmdInterface' Windows Feature.