No provider for InjectionToken angularfire2.app.options [duplicate]

Answer 1

You're not initializing your app correctly. When you import the AngularFireModule, you need to initialize there:

imports: [
    AngularFireModule.initializeApp(yourFirebaseConfig),
    AngularFireDatabaseModule,
    // ... the rest
],

More in the docs.

It used to be called angularfire2 but on the v5 release they got moved to the @angular scope. From here-on, it's @angular/fire, not angularfire2.