How can I make my Face ID to start working again

okere ~ 76% is not healthy and is probably the reason for Face ID not working. Apple recommends having the battery replaced at around 80% – so have the weak, aging battery replaced and all will be well:

iPhone Battery Service

About genuine iPhone batteries

Repair Provider Verification

(Articles found by searching Apple's Knowledge Base.)

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This link may offer the information you need. If not, please be more specific. Is there a problem with your FaceID? What is that problem?

Use Face ID on your iPhone or iPad Pro - Apple Support

okere ~ Does your iPhone XS still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health & Charging

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How to work on my face ID

Waiting please