Payment page returning a 404
I am having an issue with ClassiPress displaying a 'Whoops! Page not found' error when the payment gateway is about to be loaded. An example of the URL would be my-domain.com/order/12164/?step=gateway-process&checkout=membership-purchase
This issue started happening a few days ago, and I have tried adding the Stripe Payment Gateway to see if it was simply a problem with the PayPal Payment Plugin, but the same issue is occurring. Can you please help?