Error in Ionic App

I have an Ionic app which is working flawless in ionic serve --lab but when i build that app and install apk file in phone then it gives this error- “GET 404 (Not Found)” and warning-" Passing in credentials to $createUser() as individual arguments has been deprecated in favor of a single credentials argument. See the AngularFire API reference for details." which i have inspected in chrome://inspect.
plz help