On 30 August, 2018 issues with authentication against GoTo APIs have been observed. In rare cases the refresh of authorization tokens was not possible. The degradation was caused by insufficient performance of an API is that is provided by our API platform service provider.
Refresh tokens that were used were not process correctly. As these tokens are a one-time use token it resulted in the token being invalidated. As a result users would have to authenticate again using the OAuth flow to receive a new authorization token.
Actions to improve the reliability of the authorization API have been started and we are monitoring this situation closely.