Query System Error - Embed Power BI in D 365 Custom Workspace

Hello 

I have created a PowerBi using DirectQuery & deployed to Sandbox environment (in a custom workspace form )

Some of the reports are throwing QuerySystemError on loading. & the below error

Couldn't retrieve the data for this visual. Please try again later.

Please try again later or contact support. If you contact support, please provide these details.

I have tried refreshing by Aggregate measurements in EntityStore but still the error exists

How to solve this issue ?

Need a solution on urgent basis

Kindly help

Thanks in advance

Regards
Shanmugam