This error usually shows up in Draftsight but can also appear in Solidworks and means the serial key has been used too many times,

From uninstalling without deactivation, upgrading to a new version or switching machines having your activations used up can happen quiet easily. 

To fix the error you can go to Help or '?' icon and then to Licences > Deactivate. This works if you haven't already uninstalled the older version or still have access to the other machines it was activated on. 

If you lose access to a previous machine (hardware failure or stolen for example) then reach out to you Reseller or the team here, you'll need to confirm the key you are trying to use and your reseller can reach out to Dassault for you.