Direct answer
A wrong result requires checking inputs, mode, calibration and output separately; a working control path can still be configured for the wrong state. 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
ReversibleWrite down the selected mode, input conditions and the exact unexpected output. 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. Use a known reference input or manufacturer test and compare the result. 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. Correct the setting, calibration or component proven by that comparison.
Verify and stop safely
ReversibleRepeat with the reference and a normal real-world case. 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.