Since osCMax uses Admin access levels to control which users can access certain sections of the admin area if you need to add access to <a new file.php> within the ADMIN section you need to enable access to the file.
Open your Admin panel
Click on the Administrator Menu box
Click File Access in Menu box
Select the Catalog row in the central box
Click Store Files in right hand column
Select <a new file.php> from the drop down
Click Save