Hi Abhimanyu,
There are several check points for your to narrow down the possible root cause.
First check in Gateway server with the OData service request in the Gateway client (/IWFND/GW_Client), and see if there is any result in the http response.
If the first check returns no result as well, then you might need to set external breakpoint at corresponding GetEntitySet method of the Data Provider Class (for the sales orders entity). And refresh the page, you will get more or less some idea why there is no data returned in the backend.
Most likely the data is not retrieved in the backend due to some specific configuration for Fiori.
If you could provide some more details, it would be good for understanding the issue...
Hope this is helpful.
Cheers,
Raymond