Starting last week, I have had schedule refreshes failing with this message: Data source error{"error":{"code":"Premium_ASWL_Error","pbi.error":{"code":"Premium_ASWL_Error","parameters":{},"details...
Armando_AD I had this same error and I was able to resolve it by having my sharepoint connection run through my on premise data gateway. Once the two connections (one to SQL Database and one to Sharepoint Online using OAuth2) were running through the same gateway I was able to refresh the dataset via the service.
This does seem to be a result of a query from SQL that had merged/appended data from an excel file hosted in SharePoint Online.
I had to use append in my situation so the data would look like one dataset to keep it simple for the end user.