PHP files in modules directory returning 404

[daveJay]

We have a module installed in Prestashop that's not working because the PHP files in the modules directory are not loading. 

When you try to load http://www.grandrapidscoffee.com/store/modules/deliverydateswizardpro/test.php as a test, you get a 404. But when you do the same test with an html file it loads. http://www.grandrapidscoffee.com/store/modules/deliverydateswizardpro/test.html

Any idea what could be going on here? Is it something with the Prestashop configuration? We're on version 1.6.1.18