"!Invalid Processor" error after clicking Proceed to Pay in cart
This error happens if you are using Add to Cart buttons while your Seller Admin > Edit Profile screen has no payment services set up that can handle cart checkouts. Note that ClickBank only works with Buy Now buttons; it will not work with our Cart buttons.
If you are using PayPal, click Edit Profile and enter your PayPal Email in the space indicated, make sure the Pay with PayPal box is ticked, then click Submit to apply changes. Note that must be either the email address you use to log into PayPal or a Confirmed secondary email you have added to your PayPal account; if you enter a PayPal Email that isn't either of those, it will be removed the first time a buyer tries sending a checkout payment to it.