Our DataFlows that are reading Excel and CSV files off of Sharepoint Online folder (document library) have all begun failing to refresh this week.
Most of the errors seem to indicate some connectivity issue (or at least maintaining it)
Error: Data Source Error : The underlying connection was closed: An unexpected error occurred on a send... RootActivityId = 11af763a-f083-413e-a072-996fe7093913.Param1 = The underlying connection was closed: An unexpected error occurred on a send. Request ID: a925320e-7f06-a2d3-47ea-8558c6ff5c82.
Its's been incredibly frustrating dealing with some of these DataFlow bugs lately -- ie. hidden files bug and validating queries getting hung up.