This issue can appear if you have a proxy or content filter blocking proper access to the TakeOff Licence server location. You will be able to determine if this is the case by going to http://servername:18555 (where servername is the server where your takeoff licence is stored). If going to this location gives a warning about the site being blocked rather than the licence manager login, then you will need to get your IT to whitelist the licenceserver.
On-Screen TakeOff error Incompatible Licensing Server
Takeoff won't start because the Licencing Service is incompatible
Written by Rares Iacob