MS Exchange cannot be added to gateway

Alirezam 

Please refer the below link for the "Exchange" data source.

https://docs.microsoft.com/en-us/power-bi/connect-data/power-bi-data-sources

Please try to edit the credentials from the "Data Source Details" and use the right credntials i.e., desktop and service credentials should be same. Check with privacy level is "Organizational".

If the issue is persists, please save the file with the different name and check for the refresh and it is sucess without having any issues.

Then there was issue with exchange end.

Please check and let us know the status. Any concerns, please revert.

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venal