PDF folder source datasource issue in Gateway Refresh Issue:

PDF folder source datasource issue in Gateway Refresh : I have created Power BI report using PDF files in Folder based. If I use sharepoint location without gateway, the refresh works fine. But it is taking lots of time. If want to extract 3-4 pdf it takes 20 mins.

I have tried with one of the local folder(\\server\e\source\), it works very fast. Almost in seconds I can get the report. But when I tried to configure gateway online, could create the gateway. Issue is it not refreshing with below error. 

" Every time it shows different queires. Has anyone come acorss this issue. Please suggest. 

Regards,