The First thing to check is the form encoding type.
Make sure that the forms encoding type is set to multipart/Form-data
if the upload is still failing, edit this line:
$WA_redirectURL = "products_Results.php";
$WA_redirectURL = "";
then add the following code at line 1:
then from the bindings panel, expand the WA Uploaded Files Global Status group and add the debug info binding to your page.
post back the results after testing.