I did report this to support, they have escalated to developers. Per support engineer, this may take a while. Still waiting. Despite my requests, support could not regenerate license key or offer an interim fix.
The issue did not occur for year and suddenly started appearing. Other users on Internet report similar behavior. Must be the license server issue.
I wonder if support could issue a 10-day temporary key while the problem is getting permanently fixed. After all, they have checked that my purchase was legit and witnessed the error via remote screen share.