151: HTTP Protocol Error, 401 unauthorized

When uploading to LeagueSecretary.com, an error appears:
  • 151:HTTP protocol error, 401 unauthorized
  • League Secretary API server does not appear to be accessible from this computer
As of October 1st, 2019, BLS-2018 is no longer compatible with LeagueSecretary.com. Notices was sent from LeagueSecretary.com regarding this. Please upgrade your BLS to continue to upload.