There is an open Advisory in the O365 Service Health for Power BI. You need to be an O365 Admin to see it, so I've copied and pasted the text.
I was getting failures with no explanation for a few days - once I disconnected GA from my dataset, they stopped.
Status:
Service degradation
User impact:
Users may receive authentication errors when attempting to perform some actions that leverage Google Analytics.
Latest message:
Title: Can't perform some actions that leverage Google Analytics User Impact: Users may receive authentication errors when attempting to perform some actions that leverage Google Analytics. More info: Users may receive authentication errors when refreshing datasets which leverage Google Analytics data or when creating new queries. Additionally, errors may also be seen when editing or entering user credentials for Google Analytics. Current status: Our testing and validation of the fix continues, as to ensure that the solution will fully resolve the impact. We expect that the fix deployment should begin within the next 24 hours. Scope of impact: Impact is specific to a subset of your users who are served through the affected infrastructure. Start time: Monday, March 12, 2018, at 7:21 PM UTC Preliminary root cause: An external Application Programming Interface (API) code update has resulted in authentication issues for Power BI users with data sets that leverage Google Analytics data. Next update by: Friday, March 16, 2018, at 9:30 PM UTC
