Crystal Reports subreport data not showing from stored procedure

Message

   I have a crystal report with multiple sub reports, the data to the subreports is being passed from a stored procedure which returns to datasets. 

I need to group the data based on a parameter in the main report.

When I try to group the data in the sub report based on same parameter. It gives me a invalid grouping error. Can anyone please refer me to a link which has some explanation about such problem.

I am able to view the report in preview mode, but when I fire the report, it throws me the above error.

I am assigning the datasets to the sub reports as shown below. 

doc.SetDataSource(dstReport.Tables[0]);

                        doc.Subreports[0].SetDataSource(dstReport.Tables[0]);

                        doc.Subreports[1].SetDataSource(dstReport.Tables[0]);

                        doc.Subreports[2].SetDataSource(dstReport.Tables[1]);