ApplyDiscount Ajax endpoint

Hi, olivM. You are correct. However all of the “services” in PMPro are now loaded through admin-ajax.php now. For example, here is how that file is really called in the plugin:
https://github.com/strangerstudios/paid-memberships-pro/blob/dev/includes/services.php#L8-L15

I left those other lines in there in case someone needs or wants to access the file directly (kind of useful for debugging, or a while back we used to access them directly too).

So that line there is a bad way to find wp-load and we fixed it, but I left it in there for reverse compatibility/etc.