I have created an app and successfully tested with ngrok. The app registers itself and everything works fine. I then created a private listing in the marketplace and that seemed to work fine. I created a token and then used the link to the descriptor with token and pasted to manage apps/upload. The descriptor is accessed without an issue but when it tries to install the app I get a 503 error. On the npm start console I see no attempt to access the server. I can access both the descriptor and the /installed route from the browser with no issues. Here is the error message I get: The app host returned HTTP response code 403 when we tried to contact it during installation. Please try again later or contact the app vendor.