Hi ,
Hope you have done all basic checks like
1.Pinging host&VC ?
2.Pinging the host from vc and vice versa?
3.Trying to add with IP/Name?
4.There should not be any NAT configured between host&vc (Nat is unsupported between esx&vc)
If all are ok,please do increase the VC logging to verbose,try connecting the host,attach the vpxd/hostd logs and do mention exact date&time.That should be more than enough to know whats going wrong.
Note:Please do change the logging to normal once you are done with the log capturing.