Just upgraded my VC to 2.5 and have this error. Actually, to be fair I had a bunch of DRS/HA errors and a host that wouldn't migrate or do anything. So I unconfigured DRS and HA, then reconfigured, and life is good except for this annoying exclamation mark on my cluster. I read somewhere else that this was due to a lack of secondary Service Consoles, so I added those (on different physical NICs) but still have the error.
Thoughts?