Error "Your license for this server has expired" after importing valid license file
After importing a new license file for Nintex Workflow or Forms, the following message might still appear in the designer:
Your license for this server has expired.
Make sure that the SharePoint Timer Service is running. If it isn't start it. If it is, restart it. Perform an IISRESET.
If an IISReset fails to resolve the issue, clear the SharePoint Cache. For more information, seeSharePoint 2010 – Clearing the Configuration Cache.An IISReset should be enough to resolve this, as it will trigger the property update, however if the configuration cache has not been cleared/refreshed in some time then working through the above may be necessary.
The license data is stored in a cached Farm property and occasionally this will fail to update.