Bluetooth is used when you first launch the Mevo app to detect any nearby Mevo cameras. Once you connect to your Mevo via its hotspot or over your Wi-Fi network, the Bluetooth connection is no longer used until you disconnect from your camera. If you lose Bluetooth connectivity while actively using your Mevo, there will be no impact on your stream or recording and you will still be able to control your camera.
However, if the app is not able to detect your camera before connecting, be sure Bluetooth is enabled on your mobile device, or try turning it off and then enabling it again to reset it. Rebooting your camera can also resolve this.