This is a rule in our MP that responds to the specific event from Virtual Center - ''LicenseServerUnavailable''.
If you check in Virtual Center, what is the status of your license server? Do you see error events there?
Is the server where VMware License Server service is installed up and running OK? Is the service running, is the port (27000) open?
BTW - What version of nworks are you running?
Vice President, Product Management