When your phone connected, Android Auto asked Symfonium for its menu in a new way that also flags it as a “suggestions” request. Symfonium answers that kind of request with your recently played albums only, which is why the Home / Library / Favorites menus disappeared. Symfonium itself hasn’t changed there; this appears to come from a recent Android Auto update.
To help confirm, could you tell me which Android Auto version you have (Settings → Apps → Android Auto, version at the bottom) and roughly when it stopped working?