What to do when it says my Face ID is unavailable?

What was the result when you followed the guidance in the Related Article above your name on this page, that you were reading just before you posted here? If the Related Article doesn't answer your question please post back with more details about the issue and another user in this user-to-user forum will try to help.

Note also that Step 2. is to contact Apple support to make an appointment to get your hardware repaired.