App tries to open an URL with a custom protocol/scheme, browser protests

This app tries to handle logins through the browser with a custom "protocol"/scheme in the URI, i.e. instead of https://..., it tries to open dbnavigator://idm_auth/login?..., but the browser (Google Chrome) says "Web page not available", "net::UNKNOWN_URL_SCHEME". How do I help the app explain to the browser how to access that address?