1. First, observe whether the Mi-key app prompts that the connection is successful. If there is no prompt, or the phone does not detect the insertion of the meter key, it may be that the meter key is broken, or there is something wrong with the earphone hole of the phone, which cannot be recognized normally.

2. If you are prompted that the connection is successful, you need to use Mi-key app to set the number of keystrokes and corresponding functions. After setting, you can only respond by pressing the Mi key. If not, there is no response.

3. If it is already set, the button still doesn't work. It may be a problem with the Mi-key app, and you can reinstall the Mi-key app to solve it.

4. It may also be a system problem that causes the buttons not to respond, so you can restart the phone to solve it; If necessary, you can restore the system or upgrade the system to solve it.

5. If the key fails, it needs to be replaced; If there is something wrong with the earphone hole, you need to contact Xiaomi for after-sales maintenance.