"A problem was detected with the TrueDepth Camera. Face ID has been disabled."
Why isn’t the Face ID working?
iPhone XS
Hello,
Apple has several documents helping you with Face ID.
This Support article is specific to seeing a 'disabled' Face ID alert, and explains what to do when you see that notice or an issue with the TrueDepth camera. --> If an alert says Face ID has an issue on your iPhone or iPad Pro - Apple Support
Unless a software update solves the problem you may need to have Apple take a look at your device. Use this link to set up an appointment —> Genius Bar Reservation and Apple Support Options - Apple and this one to get a repair estimate —> iPhone Repair and Service - Apple Support