macOS 27 screen time downtime will block essential system feature

This sounds like a possible macOS 27.0 bug involving Screen Time Downtime, especially since turning Downtime off restores normal functionality. 

Since restarting your Mac has not  helped and Safe Mode only fixes Notification Centre, Iwould try the following steps before considering more drastic measures.

Check your Screen Time settings

Go to System Settings >> Screen Time >> Downtime and temporarily turn it off. Then check Always Allowed to make sure essential apps are permitted during Downtime.

Apple's guide: Change Always Allowed settings on Mac

Keep in mind that Always Allowed mainly controls app access, so it may not fix issues with Dock menus, permission dialogs, or accessories.

Review other Screen Time restrictions

Check your app limits and any Content & Privacy Restrictions. Change one setting at a time and test whether the problem returns when Downtime is enabled.

Apple's guide: Change Apps & Websites Restrictions settings

If you use Family Sharing or Share Across Devices, also check whether Screen Time is managed or synchronized from another device.

Check for macOS updates

Go to System Settings >> General >> Software Update and install any available compatible updates. If this is an operating system bug, a subsequent update may resolve it.

Apple's instructions: How to update macOS

Test with another user account

If the issue persists, create a temporary standard user account under System Settings >> Users & Groups. Test the affected features there, first without Downtime and then, if appropriate, with it enabled.

If the problem occurs only in your usual account, a user-specific setting may be involved. If it happens in both accounts, a broader macOS issue becomes more likely.

Keep the Safe Mode results in mind

The fact that Safe Mode restores Notification Centre but not the other features is useful diagnostic information, although it does not identify the underlying cause by itself.

If you need to repeat the test, follow Apple's instructions: How to use Safe Mode on your Mac.

Report the issue to Apple

Since disabling Downtime appears to restore normal functionality, I would report this as a suspected Screen Time bug. Include your MacBook Air M5 model, macOS 27.0 version, affected features, and the results of your restart and Safe Mode tests.

Using the  Product Feedback - and make it known to Apple regarding this ongoing issue

Contact Apple Support

A short screen recording showing the affected features failing with Downtime enabled and working again after it is disabled would be especially helpful.

The current version of macOS is 27.0.1. Based on your post you are running an older version, so the first step is to update your Mac to the current version.

See: Update macOS on Mac - Apple Support

This is a known issue where macOS Downtime mistakenly categorizes essential core system processes as "restricted apps", causing them to be entirely blocked while Downtime is active. Because features like the Notification Center, permission dialogs, Dock context menus, and accessory authorization rely on background system helpers, Downtime treats them as unauthorized software if they are not explicitly whitelisted.

Until Apple releases an official patch for this bug, you can use the following methods to keep your system fully functional without completely turning off Downtime:

Solution 1: Add Essential System Frameworks to "Always Allowed"

You can bypass the block by ensuring core processes are permitted to run even when Downtime is active.

• Click the  Apple menu and select System Settings.
• Click Screen Time in the left sidebar. 
• Select Always Allowed. 
• Look for and add vital system components to your allowed list:
  • Finder (which governs the Dock and desktop behavior)
  • System Settings (to ensure you aren't locked out of permissions)
  • Any specific background utilities or accessories apps you use frequently. 

More info from Apple: Change Always Allowed settings in Screen Time on Mac - Apple Support

Solution 2: Reset the Blocked System Daemons

If you find yourself stuck and unable to click "Allow" or "Deny" on prompt boxes, restarting the underlying system services will force them to reboot outside of Downtime's immediate grip.

• Open Terminal (find in Spotlight or Applications > Utilities).
• Run the following command to forcefully refresh the Dock and Notification Center:

killall Dock NotificationCenter

• This will cause both components to instantly restart, temporarily restoring functionality.

Solution 3: Toggle Off "Block at Downtime"

If you want to keep your Downtime schedule active for tracking or notifications but want to stop it from aggressively bricking system features, you can disable the strict enforcement:

• Go to System Settings > Screen Time > Downtime.
• Turn off the toggle for Block at Downtime.
• (Note: This keeps the Downtime schedule alive, but instead of aggressively locking components, it will just warn you about app limits, preventing the system-level lockouts)
• (Note also: This may defeat the purpose for which you are using Downtime, I know that it would do that with my kids.)

Sorry for let you misunderstanding. I am now using macOS 27.0.1 (Apple didn’t show .1 ……)

Sorry for let you misunderstanding. I am now using macOS 27.0.1 (Apple didn’t show .1 ……)