You may see the following error when trying to schedule a data refresh of a PowerPivot workbook in SharePoint 2016:
Sorry, something went wrong.
Or you may see the following error:
A schedule cannot be enabled for a workbook with no external data sources
The SharePoint ULS logs might show the following error:
UserProfileDBCache_WCFLogging :: ProfileDBCacheServiceClient.GetUserData threw exception: Access is denied.
This can occur when the account running the PowerPivot System Service in SharePoint (PowerPivot application pool) does not have permissions on the User Profile Service Application.
Add the required permissions using the following steps.
In SharePoint Central Administration, go to Application Management > Manage service applications, and select the User Profile Service Application. Then click on the Administrators button:
Then add the PowerPivot system service account and give Full Control:
Click OK, and then click the Permissions button:
Add the PowerPivot System Service account and give Full Control:
Click OK, and restart the PowerPivot System Service on all the SharePoint servers running this service.