Stuck in Guided Access mode after upgrading to iOS 27

Hello @pdechaine

welcome to this Apple (user-to-user) Community!

Re: "Stuck in Guided Access mode after upgrading to iOS 27"

Wondering if you have tried asking Siri to turn off Guided Access ?

If needed: Change Siri settings on iPhone - Apple Support

or

How to: Change Siri accessibility settings on iPhone - Apple Support

If help is still needed:

As last resort try a: Force restart iPhone - Apple Support to get out of Guided Access,

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Re: "Tried to triple click to get out of Guided Access and will not prompt for Passcode."

There is a similar issue on iPad being discussed ... the reply given there may or may not be helpful ?

iPad Home button fails in Guided Access a… - Apple Community

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Corresponding articles for iPhone:

To check the set-up:

For iOS 27 : Lock iPhone to one app with Guided Access

Eg: says:

Set up Guided Access

1. Go to the Settings app on your iPhone.
2. Tap Accessibility, tap Guided Access, then turn on Guided Access.
3. Do any of the following for Guided Access sessions:

• • End a session with a passcode: Tap Passcode Settings, tap Set Guided Access Passcode, then enter a passcode.
  • End a session with Face ID or Touch ID: Tap Passcode Settings, then turn on Face ID (on an iPhone with Face ID) or Touch ID (on other iPhone models).
  • Play a sound to announce time limits: Tap Time Limits, tap Sound, then select a sound or tap Tone Store to browse other options.
  • Hear time limits spoken: Tap Time Limits, then turn on Speak to hear the time remaining before a Guided Access session ends.
  • Allow Accessibility Shortcut during a session: Turn on Accessibility Shortcut.
  • Set how long it takes iPhone to lock automatically: Tap Display Auto-Lock, then select an option.

Article also says:

"End a Guided Access session"

?Depending on the passcode options you chose when you set up Guided Access, you’ll enter your Guided Access passcode or use Face ID to end a Guided Access session.

• Use the passcode: Triple-click the side button (on an iPhone with Face ID) or Home button (on other iPhone models), then enter your Guided Access passcode.
• Use Face ID or Touch ID: If you turned on the Face ID or Touch ID option in Guided Access Passcode Settings, triple-click the side button or Home button, then unlock your iPhone with Face ID or Touch ID (depending on your iPhone model)."

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The article about the option to: Quickly turn accessibility features on or off on iPhone

Eg: says:

"Triple-click the side button or Home button to turn the accessibility features of your choice on or off.

1. Go to Settings > Accessibility > Accessibility Shortcut, then select the features you want.
2. If you select only one feature, the feature is immediately turned on or off when you click the button shortcut.
3. Triple-click one of the following:

• • The side button (on an iPhone with Face ID)
  • The Home button (on other iPhone models)

To have iPhone recognize a slower triple-click, see Adjust settings for the side or Home button.

1. Tap the feature you want to turn on or off (if Accessibility Shortcut is set up with more than one feature).

Note: To add some features—like Assistive Access or Guided Access—to the Accessibility Shortcut, you need to set them up first.

You can use the Accessibility Shortcut to enter and exit Assistive Access, but you can’t use it to turn on other features while Assistive Access is active.

To use the Accessibility Shortcut while Guided Access is on, you must turn on Accessibility Shortcut in Guided Access settings."

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Article also says:

"Press the Action button

On supported iPhone models, you can press the Action button to open the Magnifier app or an accessibility feature of your choice.

See Use and customize the Action button.

Tap the back of iPhone

You can double- or triple-tap the back of iPhone to open an accessibility feature of your choice.

See Tap the back of iPhone to perform actions or shortcuts."

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Repeating the links given in the iPad discussion:

If you want to reach out to them: Apple provides an Accessibility Support Team

See: How to contact Apple for help with accessibility features - Apple Support 

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If you wish: You can send feedback to let Apple know of your experience:

If others also experience the same problem, Apple may address it in an update:

To provide feedback about an accessibility feature on an Apple product,

email the Accessibility team: accessibility@apple.com. 

All the best :-)