I have exactly the same problem.
To fix it in my case I had to use a second program to record the microphone.
I'm not sure, but I think the problem is the format of the audio, the "m4a". I say that because other programs like Bandicam record me in "Wav" or "mp3" and the audio of the microphone is heard without problem. (Without envargo it is annoying to have to use a second program for the microphone).
As a recommendation, you should add an option in ReLive to choose the codec and audio format for the microphone.
Note: I am sorry if my words sound strange, English is not my mother tongue.