Try the followings in order:
- Device Manager: View > Show hidden devices. Uninstall any greyed or flagged camera entry (tick "Attempt to remove the driver"), then restart.
- Surface Diagnostic Toolkit: Run it from the Microsoft Store and let it repair drivers and firmware.
- Surface Pro 8 driver and firmware MSI: Download the latest from Microsoft's Surface download center, install it, restart, then check Windows Update for optional driver updates.
- Settings check: Camera access must be on under Privacy & security > Camera, and the "Windows Camera Frame Server" service must not be disabled.
- Remove the September update: Settings > Windows Update > Update history > Uninstall updates, then pause updates for a week.
- System repair: In an admin Command Prompt, run
sfc /scannow, thenDISM /Online /Cleanup-Image /RestoreHealth. - UEFI check and hard reset: Hold Volume Up + Power from off to open UEFI and make sure Cameras is On. Also try a full shutdown with a 30-second power button hold.
- In-place repair install: Run Windows 11 setup from the official ISO and keep your files and apps.
- Still missing: It may be a hardware fault, so contact Surface support.