Hi imiq,

A 404 error normally means that a page can't be found. If you are receiving this on your callback page, it is possible that your settings in Worldpay's setup don't match the address of your callback script.

Log in to your worldpay administration setup and check that the callback script address listed there matches EXACTLY that of the callback script on your site (including http vs https). Note that you can have different settings for your production and test servers, so make sure that they both point to the same place.