Microphone wont work when is big angle

The microphone on this headset is designed to mute when rotated up, according to the Quick-Start Guide provided by Logitech. Perhaps your mute switch has been knocked out of alignment so it activates when the boom is lower than normal. You could try to carefully take apart the rotational part of the headset and see how the switch is activated and perhaps move it to a better position for you, or simply make the switch not functional anymore, so that the mic never mutes when rotated.