Update(Refresh) issue in Compained(Merge Query) Dataset in Power bi Cloud.

I Taking data from Two different databases (A & B)..i need join this Two database data,so i using Merge query Option(Left Join),it's working fine report aslo clear and locally Refreshing is work good ,this same report Published in our Workspace try to Update(refresh) dataset or sheduled update(refresh) not working(Failed) show the Error here-("Error during data processing in the dataset").
Anyone have a better idea plz give it.