Issue extenal page protect

I’m trying to protect an external content non-wp, but I can not work, this is my configuration:

http://www.demo.com/mywordpress/ —> where my wp-load.php
http://www.demo.com/prueba/ ——-> my page.php

in my page.php put this code:

Some content for Members who are logged in with an s2Member Level >= 1.

Some public content.

It does not work and I’m logged in, I see Some public content

But if I put my page.php within any folder on my wordpress if it works. ex.

Some content for Members who are logged in with an s2Member Level >= 1.

Some public content.

I see Some premium content for Level 2 Members.

help, we are testing this product. Thanks