Import of Excel files via Power BI Rest API

I would like to import excel files using Power BI Rest API. I can use the api to import of the excel file (https://msdn.microsoft.com/en-us/library/mt243840.aspx?f=255&MSPPError=-2147217396), the operation occure with no exceptions but the data source doesn't appear in the Power BI portal. When I imported the same file in the portal - everything goes well (I see imported data).
I see the api is still in preview mode, but pbix files are imported correctly - I would like to have available the import of excel files in the same way.