Microsoft Surface Pro No Audio on Headphones

Watching YouTube video using Firefox browser on the Surface Pro with audio coming through the built-in speakers. Plugged in headphones on the 3.5mm audio socket. Audio stops from the speakers. No audio on the headphones. Unplugged the headphone, audio is back on the speakers. Strangely enough, this doesn't happen on my other laptops and tablets.

The theory here is that when Firefox is first started, it chose the built-in speakers as the default audio device. Play YouTube and it routes audio to the speakers. When you plug in the headphones, Windows add a second audio device and makes this the default audio device. However, Firefox is not aware of this and continues to send audio to the speakers, which are now muted by the introduction of the headphones. Most likely a hardware/firmware/driver issue somewhere?

In my particular case, this was fixed by shutting down Windows, plugging in the headphones, and booting up. Windows installed some updates during the reboot, so the issue might've been fixed with some new driver, or maybe it just needed a reboot.

A few things you can try if the above didn't work for you:

• First of all, make sure the headphones are not the problem. You never know. Try them out on a different laptop (or phone).
• Have a look at the headphone plug. Give it a clean if it's dirty.
• When you plug in the headphones, does the audio device switch from speakers to earphones? Check by hovering or clicking on the audio/speaker icon. If it's still on speaker, right-click the audio icon, then Open Sound Setting. Choose earphones as the output device.
• If that still doesn't work, try the "Troubleshoot sound problems" option. Windows will most likely reconfigure or reinstall or reset the audio driver, which should fix it.