IPHONE users are complaining that Face ID has stopped working on their handsets, The Sun has learned.
The mysterious issue means that Apple's face unlock technology no longer recognises faces – forcing users to rely on passcodes instead.
Apple 4 Face ID lets you unlock your iPhone with your face – even in the dark
The Sun has discovered dozens of reports about the issue across Twitter, Reddit, Apple's support forums and fan forums.
Most of the complaints seem to be from users with the iPhone XS Max (which costs between £1,099 and £1,449), but other handsets have also been named.
Face ID is Apple's facial recognition software, introduced last year as a way of safely verifying your identity.
It's only available on the iPhone X, iPhone XS, iPhone XS Max and iPhone XR right now, because it relies on sensors built into the actual handset.
Apple 4 Users are reporting a strange error message when attempting to use Face ID
On Reddit, one user wrote: "I got my XS Max a few weeks ago, and Face ID has been working wonderfully until maybe yesterday or this morning.
"So, when I just tried to start over and reset my Face ID, I got a message saying 'Face ID is not available. Try setting up Face ID later'."
Another user on Reddit posted an image of the error message, seemingly confirming the issue.
One user on the MacRumors forum linked the issue to the new iOS 12.1 update – although we've been unable to verify this is the case.
They wrote: "I have an XS Max and just upgraded to 12.1 about an hour ago.
"Now my Face ID won't work, I reset it, and it says Face ID not available."
Dozens of users have posted similar complaints to Twitter, some of which date back several weeks.
Apple 4 Frustrated users have taken to Twitter to complain about Face ID
One wrote: "My Face ID is not working any more. Tried setting it up 20 times and it doesn't want to recognise my face. I have the XS Max."
Another said: "It worked at first but then stopped working to unlock my phone. So I did 'reset Face ID' and when I try to set it up, it says 'Face ID not available'."
We found at least 30 threads on the official Apple Support forums complaining about an identical issue in the last week alone.
The Sun was also able to confirm the issue existed on an iPhone XS Max running iOS 12.1.
Fortunately, there is a fix that seems to be working for at least some users.
Apple 4 Face ID works using sensors that are built into the "notch" at the top of your iPhone display
How does Apple's FaceID tech work? Apple's facial recognition system for the iPhone X isn't massively complicated. Here are the steps your phone takes: The phone will use various sensors to work out how much light it needs to illuminate your face.
It then floods your face with infrared light, which is outside the visible spectrum of light.
A dot projector will produce more than 30,000 dots of this invisible light, creating a 3D map of your face.
An infrared camera will then capture images of this dot pattern.
Once your phone has all that info, it can use your face's defining features – like your cheekbone shape, or the distance between your eyes – to verify your identity.
It computes a score between 0 and 1, and the closer it is to 1, the more likely it is that your face is the same as the one stored on your iPhone.
Apple says there's a one-in-a-million chance of someone else getting into your iPhone with Face ID, although the system has been tricked with twins.
Still, it's arguably better than the alternative: Apple's Touch ID fingerprint scanner has a one-in-50,000 chance if being fooled.
How to fix iPhone Face ID 'not available' bug
Several users posting online have suggested that performing a "soft reset" on your phone.
The Sun has been able to confirm on a review device that this technique does resolve the issue.
You'll need to press the Volume Up key then release, press the Volume Down key then release, and then press and hold the Power button until you see the Apple logo on-screen.
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This won't wipe any data from your phone – it's simply a reboot.
It's not clear how many users are affected.
We've asked Apple for comment and will update this story with any response.
Have you experienced any issues with Face ID recently? If so, let us know in the comments!
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