Hello. I’ve been signing in with Face ID for a long time. I just changed my phone and I realized that I’ve forgotten my master password. The app won’t offer the chance to sign in with my face. Is it possible to restore the Face ID to allow me in?

No, if you have no master password you will not be able to activate FaceID.

I second @AnakinCaesar. If you have forgotten your Master Password, there is no way to restore Face ID access. Face ID is a convenience feature, but the Master Password remains the primary method of authentication. If you don’t remember it, you’ll need to reset your vault and set up Enpass again.