Same problem. Works great last 5 days before yesterday. All my 5 dashbords stop reshresh data from SSAS. My users in panic ;-) now i'm back my users to "old" Datazen dashboads.The secon problem (i think related to first one) - Power BI stop refresh new measures added in SSAS tabular model. (Full process cube, wait 15 min and refresh page - nothing change).
In trace log SSAS - no erros! EffectiveUserName contain correct value. But when create new datasource (Get Data), it contain all schema changes in SSAS. Please check what happens 2 days ago in Power BI server.
Similar case I have observed while working with Power BI REST API. Dashboard gets updated instantly but report fails to refresh automatically unless refreshed (F5) manually. If this is the case then motto of real-time Dashboard won't serve the purpose.