You are using a wrong adapter.  That splitter cable allows 2 headphones for listening, not one headphones and one Mic., and the plug has only 3-pole connection, lacking a circuitry for Mic. You will need an adapter similar like this one, which has TRRS 3.5 mm plug (4-pole) connecting to 2 separate plugs for headphones and Mic.   [IMAGE]
I am having an issue using the below products on my dell Inspiron 15 Gaming 7567 laptop. The following are some troubleshooting I did so far: I did install the latest Realtek audio and Mic is enabled in the setting. When I plug them (sony headphone and boya by-mm1) in using the splitter, in the pop up I choose "headset". the sony headphone works fine when I play audio, but when I test the mic, only the laptop's "internal" mic works and not the external. If I open Waves Maxx audio pro, the output device says "internal speaker" and is greyed out. Also in the task manager > startup, the following are all enabled (HD audio background process, Realtech HD audio manager, Waves maxxAudio services applications).   Products: Mic: [URL]  Headphone: [URL]  Splitter Cable: [URL]  [IMAGE][IMAGE][IMAGE]  
Inspiron 15 Gaming 7567: External Mic not working