truedepth problem - face id disabled

That's a hardware fault. Make an appointment at the genius bar.

I mean, the true depth camera system is no working correctly.

In order to be used for security, it has to be functioning at a higher level than that used for animoji.

Make an appointment at the genius bar and get it fixed / replaced. It should still be under warranty.

The warranty follows the phone in most cases. Since all iPhones are less than one year old, it's under warranty. The only time I've heard of anyone requiring proof of purchase for warranty service is in countries where Apple is not the service provider.