For your reference, here are some troubleshooting steps:
1. Check whether the volume of your phone is too low, thus resulting in no sound;
2. Check whether the Mi Home/Xiaomi Home APP has the permission to use the microphone (recording) of the phone, if not, turn on the relevant permissions in the settings of the phone.
We hope the above methods can help you solve the problem. If your problem still exists, please contact the local after-sales service center for further assistance.