Hi Colin Williams,
The fact that the microphone works through the USB dongle is useful because it gives you a way to isolate the problem.
Please try:
- Another 3.5 mm headset with a mic on the laptop.
- Your current headset via 3.5 mm on another device.
- Check that the 3.5 mm plug is fully inserted and that the jack is clean.
If multiple known-working headset microphones aren't detected through this laptop's 3.5 mm jack, a hardware issue with the jack becomes more likely. In that case, the USB adapter remains a practical workaround, or the laptop manufacturer/support service can check the jack itself.
Hope these tests help you pinpoint the cause.