So I setting up an old Desktop PC as a Windows 2012 R2 Essentials Server. I wanted to use WiFi to set it up as I am not near a network port, but every time I enabled the disabled WiFi adapter it kept disabling itself again. Even using a USB WiFi card didn't work so a little poke around and it was a simple fix to get working.
You need to install the Wireless Lan Service in Server Features.
So Run Server Manager -> Manage (Tab) -> Add Roles and Features
Click through the wizard until you get to Features Section and tick "Wireless Lan Service" (near the botttom).
Might need a restart.
OK but wait the WiFi adapter is still disabled. Quick check in Services:-
Server Manager -> Tools (Tab) -> Services
and I noticed the WLAN AutoConfig was not started. Start this and bingo you can now connect using WiFi.