When trying to import from Google Drive, the following error is shown:
There was a problem retrieving the token used to identify you with Google Drive.
Any error code ending in -257
This happens when there is a problem with Google Drive concerning authentication services or a network problem between you and Google Drive. It is possible that their server is not responding correctly or that your network has issues and Sharegate cannot access the information needed to communicate with Google Drive. Sharegate needs a token to identify you to Google Drive, but in that case, the token cannot be retrieved and Sharegate cannot continue without it.
The main solution is to wait and try again later since this is a problem within Google Drive. Since it can also be caused by a network problem, make sure your internet connection is active or contact your network administrator to ensure everything is up and running.