Sound appears to no longer be working. System shows that speakers are playing sound within the control applet.
Testing the speakers via playback options does not work, but displays green bars.
Device still does not play sound even after full reinstall.
Issue seems to be related to UEFI, which cannot be restored.
Detaching the type cover/touch cover 5 times. (Yes, it really works.)
Try inserting a pair of headsets and play sound.
Set speakers to default device (if its already default, make headphones default and then cycle through the two.)
Unattach the headphones while it was set to default device.
Reboot the surface
Sound should now be working.
Disclaimer: This is not an official fix, but I can vouch that I did have this problem and contacted Microsoft Support and they arranged a hardware replacement due to corrupted UEFI. It's covered automatically for one year for free. However, with those steps I managed to fix it myself.
It was an odd issue for me, because restoring the computer didn't work.