Can this Face ID be fixed at home

This document is specific to seeing a 'disabled' Face ID alert, and explains what to do when you see that notice. --> If an alert says Face ID has been disabled on your iPhone or iPad Pro - Apple Support

Do as the document instructs.

No, you can't resolve that at home if the issue is pertaining to the genuineness of the camera.

Camcharlow ~ What model of iPhone is it?...

Settings > General > About > Model Name

And what version of iOS is it running?...

Settings > General > About > Software Version

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