Two years ago I had exactly the same problem on the same laptop, under the 'same' Windows 10, and I solved it then by way of the following path: 'Control Panel' > 'Realtek HD Audio Manager' > 'Device advanced settings' > 'Separate all input jacks as independent input devices'. After recent Windows 10 updates, my Toshiba laptop's in-built microphone stopped working whenever anything (e.g., external speakers) is plugged into my laptop's audio jack.
