a. You have not powered on your camera.
b. You have not turned on Bluetooth on your phone.
c. You have not pressed Agree on the camera to allow pairing.
d. Please check if the camera is currently paired with another phone. If so, please unpair or turn off the Bluetooth of that phone.
e. If you are an Android user (with Android 6.0 or above), please check YI-M1 Mirrorless Camera App, navigate to Settings -> Permission and make sure your Location Access is enabled.