Direct answer
A complete failure should be separated into power or eligibility, the external path, and the component itself before any reset. For iPhone Face ID, first clean the sensor area, remove obstruction and test unlock plus one supported app.
What this covers
- iPhone Face ID with this exact failure state
- Diagnosis across attention/appearance and screen protector versus camera obstruction and hardware
- Customer-accessible observation, settings and external components
What it does not cover
- ×A displayed manufacturer error code with a different documented meaning
- ×Live electrical, sealed-system, internal battery-cell or gas repair
- ×A claim that every model exposes identical controls
Capture the exact failure state
ReversibleRecord whether the feature is absent, disabled, powered but unresponsive, or showing a message. Expected behavior: recognize the enrolled face through an unobstructed TrueDepth system under supported conditions.
Isolate the component boundary
ReversibleClean the sensor area, remove obstruction and test unlock plus one supported app. Test the simplest supported configuration with unrelated accessories and optional services removed. Boundary to separate: attention/appearance and screen protector versus camera obstruction and hardware.
Correct only the proven cause
ReversibleUpdate, reset and re-enroll Face ID only after passcode and app credentials are available. Restore only the failed prerequisite or path; do not change working layers.
Verify and stop safely
ReversibleRepeat from a cold start and complete one normal use. Service after impact, liquid or a TrueDepth unavailable message that persists.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Exact questions
Common follow-ups
What should I check first when iPhone Face ID has this problem?+
Clean the sensor area, remove obstruction and test unlock plus one supported app.
Why not factory-reset immediately?+
The useful boundary is attention/appearance and screen protector versus camera obstruction and hardware. A reset can erase state without proving which side failed.
When should I stop troubleshooting?+
service after impact, liquid or a TrueDepth unavailable message that persists.
Answer for the exact device and software version shown above.