We have been getting barraged with a sudden onslaught of scheduled refresh failures for the past couple weeks. Projects are failing at random and throwing the following error message:
Unable to connect to the data source undefined.
No error message available, result code: E_UNEXPECTED(0x8000FFFF).
The error message is attributed to a certain dataset, but it is always random as to which one fails. Our datasources are a mix of excel files and access .mdb files. The .mdb files seem to be the culprit.
The same error occurs randomly in Power BI Desktop. The only solution there is to close and reopen the project file and then it will work.
Sometimes kicking off a manual refresh in the online service will be successful, but often it will just throw the same error message. When the next scheduled refresh hits, sometimes it will be successful. The failures just seem very random.
All our reports are set to refresh daily. Most of them are run off the same datasets. They drive multiple dashboards and are published to multiple apps so its really annoying when they start acting up.
As far as troubleshooting, we have updated our gateway to the most recent version. I've also removed all the projects and datasets from the online service that were throwing the errors and republished them. This seemed to help a little, but overall the problem is still there.
The project files and datasets themselves have not undergone any major changes. These reports have consistently refreshed fine for months. The problems just seemed to start out of the blue.
Any thoughts would be appreciated. Thanks!