Hello Aaryan Barot, thanks for posting this in our community.
If your mic is not working with a splitter, first check the type of splitter you are using. An audio-only splitter that splits left and right audio channels will not work for a microphone. You need a TRRS to dual TRS splitter, which is a 4-pole to 2x 3-pole adapter, often labeled as a “headset splitter.”
Make sure the connections are correct. Plug the headphone jack into the headphone port and the mic jack into the mic port on your PC. If your PC has a single combo jack, you will need a TRRS-compatible splitter or consider using a USB sound adapter.
To rule out hardware issues, test the splitter and headset on another device such as a phone or another PC. If the mic works there, the problem is likely with your PC’s audio jack or settings.
Kind regards,
John Oli