payment profiles error

I bought an add-on that hasn't worked since I got it, not here to complain about that. I'm new to XF and would like to figure this out since the guy who made the add-on has been M.I.A for 3-4 months so I need to get this figured out. Using the default payment profiles I started to get a bit of...

Unable to delete payment configuration and display the following error： ErrorException: Fatal Error: Call to a member function getPurchasablesByProfileId() on null src/XF/Admin/Controller/PaymentProfile.php:149 Generated by: GTAForce Nov 6, 2018 at 20:00 Stack trace #0 [internal function]...