Headset Mic Not Working

Hello!

So I have recently purchased a new laptop (ASUS GL551-JW running Windows 8.1 64bit) and am having some troubles with my headset.

I own a Turtle Beach X12 head set and have purchased a combo adapter for the combo mic/headphones jack on the laptop.

When connecting my X12's to the laptop through this the sound comes through fine but I cannot get the mic working!

I have tested with my phone and it works perfectly so it is not the cable or the headset.

I have had a look in recording devices with show disabled/disconnected devices on and can only see the build in mic which does not pick anything up when I plug in my headset (doesn't pick up anything from the built in mic either).

When checking playback devices I did notice that no additional playback option comes available when I plug in my headset and that the sound comes through the same default 'Speakers' device it does when nothing is plugged in. However the sound is coming through the headset fine and not the laptop.

I have had a look around and cannot find any reason why Windows is not picking up my headset mic!

Any help would be greatly appreciated!