Between 2am and 3am UTC on August 29th, the authentication of GoTo APIs was degraded. During that time, response times of the API increased and the refresh of authorization tokens was not possible. The degradation was caused by an outage of an API that is provided by a service provider.
Refresh tokens that have been used during that time were not processed correctly. As the refresh token is an one-time token, this led to clients not being able to refresh their previous authentication. Users have to authenticate again using the OAuth flow to receive a new authorization token. We are working on improving the stability of the authorization API in order to prevent future degradations.