When WP Simple Pay Pro is installed and activated, two pages will be generated: a Payment Success Page and a Payment Failure Page.
By default, after payments made through WP Simple Pay Pro succeed (or fail), the payer will be redirected to the appropriate page.
These pages can be edited like any other WordPress page, but you can also select existing pages for either option in your WordPress admin under Simple Pay Pro → Settings → General (tab).
You can also change the payment success page at the form settings level. Visit Simple Pay Pro → Payment Forms → (Your Form) → Payment Options.
There are 3 options to choose from here. Global Setting will use the setting you have saved in the main settings. Specific Page will give you a dropdown to select the specific page on your site you want to redirect to. Finally, Redirect URL will allow you to type in a custom URL into a text field to use as the redirect.
Make sure the
[simpay_payment_receipt] shortcode resides on the Payment Success Page. To customize this shortcode output further, see how to configure the payment confirmation display.
Also, make sure the payment confirmation page is excluded from any site caching enabled by your web host.