Does the normal front camera work? Or does it show error?
If camera itself doesn’t open → driver issue.
If camera works but Windows Hello doesn’t → IR camera issue or Windows Hello corruption.
Open Device Manager > Right click Surface IR Camera > Click Uninstall device
Restart the Surface. Windows should reinstall it automatically.
Download and install driver of Surface Pro.
Settings → Accounts → Sign-in options → Facial recognition
Click: Remove > Restart
Set it up again
Shut down
Hold Volume Up
Press Power
Release Power but hold Volume Up
Check if:
Camera appears in devices section
If missing, there too → possible hardware fault.