Yes, our app can work with the ShopPay express checkout button from the product page. You need to enable this setting from the General settings section.
https://imagedelivery.net/cpyRmB-4Qzn5-ySmAHXmxA/6d36f0a7-696d-4783-19d7-4aa131fcbd00/public
Note: the app will not work with any express checkout buttons from the Cart page (only product and checkout page)