You will see this error if Xink App finds that a domain token has been set, for example through mass deployment.
The domain token can be deleted on a MAC machine by running this command from Terminal.
1. Check if the access code is grayed out
2. Quit the Xink client
3. Open the terminal and run this command defaults delete com.emailsignature.Xink domainToken
4. Restart the app and enter the access code.