Please make sure your controller is not only connected to your app but also check your phone's bluetooth settings to make sure it's both paired and connected.
Android: The app is only needed for Forcite specific functions like video recording and repeat navigation. Other features such as media stop/start and volume control will function without the app being on.
On some phone models and versions of Android, if the phone is locked, the volume buttons will only change audio volume if depressed while navigation audio is actually playing. To do so, press the controller's navigation button, then depress the volume button to change the volume while the audio is still playing. Press and hold will repeat the up or down volume command.