Dear user,
You may try the methods below to see if it helps:
①If the app quit working, it is suggested to clear the pairing record of the BTR3K in your phone. Then reconnect it to your phone and try again.
②For the iOS version: the first time to enter “Bluetooth device control”, short press the power button of the BTR3K to finish connection, and then click “Cancel” and return to “Bluetooth device control” menu. It will be connected successfully. At this time, click BTR3K to execute relating operations.
③For the iOS version: if the BTR3K did not show up in the “Bluetooth device control” list, click the “Refresh” icon in the upper right corner, or quit the app for a while and then reenter it.
Best regards