Can't upload report to report server on Microsoft Windows Server 2012- This is a unique problem

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I installed The latest version(March 2018) of Power BI Report Server(Evaluation) on my Production Server(2012 R2- Standard) and installed the Power BI Desktop optimized for Power Bi Report Server - March 2018 on my pc(Windows 10). When I attempt to upload a report to the server(2012 R2- Standard), I get this error

"There was an error uploading your .pbix file. Verify that this file has not been corrupted and that the file extension matches the format of the file."

There is no problem with the file since I am able to upload it to a local report server on my PC (Windows 10). This error only occurs while I am attempting to upload to the Power BI Report Server on my server(2012 R2- Standard).

Any help?

As suggested by another user on this forum, I have changed the service account in the report server configuration manager from virtual service account to network service but the problem persist.