Hello, the main reasons are:
1. Please check whether the Bluetooth list of the device has not been refreshed;
2. Whether they have been paired and connected to other devices.
Solution
1. Refresh the Bluetooth list of the device;
2. Press and hold the MFB and ANC button for more than 3s at the same time to clear the pairing list and restore factory settings; refresh the Bluetooth list of the mobile phone, wait for the Bluetooth name of the device to be searched in the Bluetooth list, and click to pair and connect.