Error Occured while refreshing my dataset after Publishing

Dear Community 

I would need your support:

the situation is the following: I have created and published a report on my organization workspace, and scheduled a refresh of my report every day morning. however i keep receiving below error message. 

The source I am using is a power BI dataflow with our own system data and a sharepoint which has many excel file that I Append all together 

Now I have to refresh on my desktop app all the time and publish it again 

Please support!!!

Thanks and regards