I downloaded your corrected login.php file, then uploaded the current files.
On login, it denies access to 'SalesCredentials_results.php' (URL in PM)
It should allow access to that page. I think the rule is wrong, but I don't know how to correct it. I've tried both of these with the same result:
<?php echo ($_SESSION['SecurityAssist_UserLevel']); ?>
<?php echo ($_SESSION['UserAccess']); ?>
You mentioned an AccessGroup session variable, but I've been using the Access Pages manager. Is this the problem?