In my case we have 1 VC (windows based) with 2 PSC (appliances) we got these error suddenly
Cannot synchronize host (host name) License not available to perform the operation.
Cannot complete the license assignment operation cannot assign a license to "Host" XXX Make sure the License Service is available
Investigation:- I found there was issue in time between PSC and VC
Solution:- Correct the time on PSC and restart vpxd , issue got resolved.