Microphone Hal Example didn´t work

Hi there
I ran the sample Microphone program from the Matrix Creator website.
https://matrix-io.github.io/matrix-documentation/matrix-hal/examples/microphone/

I also get 8 raw files output but after converting them to wav files I still don’t hear anything.

The same happens with the simple example program from the Matrix github page. There it also records a 5 second file but when I play it back I again hear nothing.
https://matrix-io.github.io/matrix-documentation/matrix-creator/resources/microphone/

I would be happy if someone could help me