Getting "Table is not connected to the data" error despite RegisterData called

Hello, I have a report with several data sources defined. I am registering the data but I get a Table is not connected to the data error. Can anyone help?

using (var report = new Report())

           {

               report.Load("Reportes/Reporte presupuesto.frx");

               report.RegisterData(presupuestoPdf.Referencias.ToList(), "Referencias");

               report.RegisterData(presupuestoPdf.Conceptos.ToList(), "Gastos");

               report.RegisterData(presupuestoPdf.Liquidacion.ToList(), "Liquidacion");

               report.Prepare();

               using (var stream = new MemoryStream())

               {

                   report.Export(new PDFSimpleExport(), stream);

                   return stream.ToArray();

               }

           }

       }