Hi YI.ZHANG,
Thank you for posting in Microsoft Community.
I understand that you're having trouble logging in to your Surface Pro 8. It's possible that the face recognition feature may have been disabled or there may be an issue with the camera.
Here are some steps you can try to resolve the issue:
- Restart your Surface Pro 8 by holding down the power button for 20seconds. Then try logging in again using face recognition.
- If that didn't work, try signing in with your Microsoft account password instead. Select the sign in options and select "Password" to sign in with your Microsoft account.
- If your able to sign in with your password, set up the facial recognition again by going to Settings > Accounts > Sign-in options > Windows Hello Face > Set up or improve recognition. You may check other suggestions from this article Troubleshoot problems with Windows Hello on Surface - Microsoft Support.
- Then set up a PIN or reset it if you don't remember your PIN, you can reset it by going to Settings > Accounts > Sign-in options > PIN > I forgot my PIN.
Let me know if you're able to sign in with your Microsoft account password.
I hope to hear back from you.
Kind regards,
Lavenia