Enable iOS Background Bluetooth

We have an app uploaded on the App Store.
The backend is Node.js, the frontend is Flutter, and the server is Contabo.

We have a feature in the app where the user must enable Bluetooth to appear via the camera in our app.

But the problem now is in iOS in the background. When User A + B enter the app, open the camera, and enable Bluetooth in the app, everyone can see each other. If User B exits the app, they disappear from User A's camera.

Even if Bluetooth is working, we want Bluetooth to work in the background even if the user exits.

Everything is working for us, all codes are fully uploaded, and the feature is working fine. But our only problem is that Bluetooth turns off in the background.