(HELP) Microphone Not Functioning Properly

The microphone is not able to receive input from the actual microphone, however (oddly enough), it only works when I directly talk through the speaker in the headset. As you can probably imagine, it’s not very practical to do that whilst playing a game. I have both the microphone and the speaker cables plugged in (using a Windows Dell PC), so what do you suppose it the problem? Thanks in advance!