My iPhone X Face ID isn’t working

The support article you came here from should provide you with the steps needed to try to resolve this issue. Have you tried them all yet? If so, and they didn't help, I suggest that you contact Apple Support directly. To do so, simply

select the "Support" link in the lower left-hand side of this forum's web page.

Follow the steps in the support document you posted from. If nothing works, then do as suggested and take the device to an Apple Store or Authorized Service provider near you so they can diagnose and repair it.