ReportViewer in local mode not displaying data from table in chart

I am adding a table as the datsource to a ReportViewer displaying a chart and running in localmode, but the chart is empty. 
The table definitely contains populated data rows.  The code is:
 
string connStr =  "server=localhost;Trusted_Connection=true;database=MDX_Extract";
SqlConnection conn = new SqlConnection(connStr);
DataSet ds = new DataSet();
using (SqlConnection conn = OpenSqlConnection())
{
SqlDataAdapter da = new SqlDataAdapter(sSQL, conn);
da.Fill(ds);
       da.Dispose();
}
 
ReportViewer rV = FindReportViewer(activeReport);
ReportDataSource rds = new ReportDataSource("DataSet1", ds.Tables[0]);
ReportViewer1.LocalReport.DataSources.Clear();
ReportViewer1.LocalReport.DataSources.Add(rds);
ReportViewer1.LocalReport.Refresh();
 
Any ideas what's happening?
...