I recently bought a 3.5mm 4 Pin to 2x 3 Pin 3.5mm headset splitter adapter. Like this one: Headset splitter on Amazon.
When I plug headphones jack and microphone jack into the splitter and splitter into my macbook pro 13" (2015) it only recognizes a new output audio device. But in sound preferences in input tab is only one input device - Internal microphone, type: Built-In.
Actually I think it worked fine for the first time I've connected it, but after some restart or disconnecting the splitter, it never worked as it should.
Any ideas or similar experiences?