Mic and the headphone work only when I make a pressure on the screen.

Hello, I got an HTC One M9+ device. When making phone calls, people can hear me only when I shift to the loudspeaker. The other mic and the headphone don’t work at all. But I realised that, when I make a pressure on the right bottom of the screen, as long as I keep pressing, they both work fine. What may be the reason, any guesses?

(Sorry, I had to choose M9, because M9+ is not listed in this site.)