The front or siri microphone works only few times

I’ve replaced my iPhone 6s plus front camera flex cable, Everything works again apart from the front microphone. When I make a video with the front camera, I sometimes hear very low audio, and sometimes hear the audio correctly, and, when I try to configure Hey siri the “audio wave” moves only slightly meaning that Hey Siri doesn’t recognize my voice, instead, when I press the home button to talk to Siri, the microphone works only for the first 5 seconds, after that Siri stops listening. same with the vocal dictation.

So what’s the problem with that microphone? Is it faulty or have I mounted it badly?