Stored Procedure Call & Data Connection for .aspx page

I have a stored procedure in SQL Server, a SQLDataSource on my form, and textboxes, DropDownLists, and a button all for inserting one record into my databases... something is not working... I'm really rusty with my old data access code... any ideas? Probably a problem in the bold copy.
SP:
USE [TrackIT]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[InsertTransaction]
      
       @PO_Number                      VARCHAR(50),
       @Buyer_Initial                  VARCHAR(50),
       @Quantity          ...