Unable to unlock my iPhone through Face ID

I bought my phone from swappie company. When I first bought it, there was no problem. I bought it a month and a half ago. I have the phone locked on my face. For a week now, I have been trying to unlock the phone on my face, but it won't open. I tried to reset the face ID, but it didn't work. I restarted the phone, but it didn't work. The phone is updated to the latest version. I have iPhone 13 Pro Max

What's the problem?

[Re-Titled by Moderator]