Mobile voice chat problems can be caused by a different reason. It could be a problem with technicality such as soft- hardware. As well it could be a problem with the setting.
Common Problems that appear with call of duty especially with “Mobile Voice chat not working” such as being dropped from the voice chat after joining, cannot join team or group voice channel, mishearing problems, and teammates are muted but cannot be un-mute. You must not be silenced from a penalty, for that you will be unable to use voice chat.
Such problems can be easily solved by checking the 4 voice chat settings. Volume levels, Voice Chat is set on, Suspend Voice Chat is set to Default and Voice Chat Channel is set to Default.
Parental controls can prevent the voice chat, make sure it has been disabled. As well as plugging in the microphone, and unmute it.
Make sure your Default Device is set up correctly in Windows and selecting Recording Devices. For resolving any compatibility issues you need to update your drivers and operating system.
In another way you can enter to Call of duty settings, you will be given a table of choices, where you tap on audio and graphic. Select the audio, and then move to Voice Chat and Microphone and enable them, and on the right side you can control the volume of the voice chat “low-high”. Yet for the Microphone. Lastly, you need to restart your device so it can be set all over again.