Normally I would be singing the praises of Power BI but this issue is beyond infuriating as it is not something I am able to workaround. I have had to revert back to July's version as neither August/September will complete a manual refresh.
One report of mine for example that would normally take around 20 to 30 minutes to fully update using multiple sources including use of dataflows - Dynamics CRM (OData) & Navision (SQL), & Direct Query) was initiated at 5pm yesterday and was still stuck on this message at 8am today. I had to cancel it again as it causes company wide system issues after the evaluation stage.
Direct Query to MS SQL Server now works on the older version, but CRM (I expect I'll be waiting all day to get past Evaluating... for one table). Also the "Data last refreshed" mouse over tooltip appears to be missing from September's version when looking at tables in the Fields listing.