Headset either Xbox and computer monitor

My son recently got a computer monitor, mouse, and keyboard to connect to his Xbox one. He loves the set up but now his headset will not work correctly. He can hear but the mic does not work so he can't talk to his teammates in the game. Is there a solution to this or a specific headset he needs? He previously plugged his headset into his controller, but this isn't needed or functional when using the keyboard and mouse. Any suggestions on how to resolve this?

:)