Gateway Error - Cannot be added to gateway

I took my reports off the service, rebuilt the dataflow and uploaded them again. It seemed to have fixed the issue, still not sure what caused the failure but the classic on/off approach has saved the day again.

Thanks.

I took a different approach. Too troubleshoot, I turned off all the 'include in report refresh" in power query for the tables connected to a dataflows. Uploaded and to and check to see if refresh worked. It did. Then I turned them all back on, and everything worked.

Dataflows are still in beta, seems to be a bug. But at least now I can combine data from multiple excel online spreadsheets.