Unable to Post/Upload excel file using Post Import Rest API

[Anonymous]

Hello

I am attempting to upload a excel file to my group using the Post Import rest api from the C# SDK as well as the raw POST method - but both of them result in the "Bad Request" error. 

https://docs.microsoft.com/en-us/rest/api/power-bi/imports/postimportingroup

It works fine with a .pbix file - but is failing with a excel file. I have made sure that the excel file has data formatted as table. Why is the POST IMPORT in Group API failing with excel file upload?

Thanks

Aj