to troubleshoot, make sure that page does not redirect after performing the upload, then add the following code at line 1 to turn on error reporting:
<?php
error_reporting(E_ALL);
ini_set('display_errors','on');
?>
then open the bindings panel, and expand the uploaded files global status, add the debug info binding to your page.
then add the following code before the closing body tag:
<?php var_dump($_FILES); ?>
post back the results after testing the upload again,