@song1 that means you sent us wrong store url when you placed the order, the message shows that you sent us url for the store that doesn't exist. But don't worry, please just contact us directly with your proper store url and we will send you a proper link to install the app immediately.
@MagicTech please contact us directly and send us printscreen image of the error. This error can not be related to our app because our app just automatically inherits payment methods from Shopify original checkout. If you send us printscreen image we will be able to tell you what exactly can be a problem.