This is an obscure issue caused by elevated levels of security on corporate firewalls. By default, they stop external web sites talking back to computers on their network, for obvious reasons.
This is the error message dialog box:

The Fix
To access our license server, all of the below URLs must be added to the whitelist of allowed sites on the firewall:
us.applicad.com www.applicad.com applicad.com crm.applicad.com ocsp.digicert.com
Faulty Company ID
Another problem observed lately, that presented the same message was the failure of a particular License or Company ID. Generated a new Company ID and it worked. So if all else fails, generate a new Company ID and use that.
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