Is Order Received Page

I am using the trial version of the custom thank you page plugin before deciding to buy but it appears that replacing the default confirmation page breaks the hook into the WordPress filter woocommerce_is_order_received_page:
https://docs.woocommerce.com/wc-apidocs/source-function-is_order_received_page.html#211 This filter should return “true” on the custom order received page.

Is there a fix for this please?