Xbox One headset/mic help

Old git here. Last computer game I played was on a ZX Spectrum. My son has an Xbox One and can't get the headset to work. Ive tried but am sadly no use to him. I don't think there's anything wrong with the hardware, as it does register a quick beep in the headset when you press the mute button. It must be something simple, but it's beyond me. Anyone got any suggestions?]

Sorted now, in case anyone was wondering! Don't ask me how.