Plugin not showing for members

I installed the supported plugin and it shows in administration area, i can configure it and everyhing.
But members can't see the "Premium" area to be able to upgrade or pay, and when i visit the .../wp-admin/supporter.php, it gives me the error "Fatal error: Call to undefined function supporter_output() in .../wp-admin/supporter.php on line 34".
This error doesnt show when I, as admin, connect and visit the wp-admin/supporter.php.

Any ideas?

thank you for your help :slight_smile: