Microphone doesn’t work on my iPad

See >>> If the microphones on your iPad aren't working - Apple Support

Have you allowed your Apps to access the microphone? If permissions have been denied, the App will record without sound from the iPad microphone:

Settings > Privacy & Security > Microphone

Each App that requests access to the microphone should appear in this list. To enable use of the iPad microphone, the corresponding entry for the App must be set to ON.

More information about granting access to hardware features can be found in the iPad User Guide - the relevant page being here:

Control access to hardware features on iPad - Apple Support