How to fix iMessage and FaceTime not working after macOS upgrade on both Mac and iPhone?

Re: Latest Mac OS upgrade causes iMessages and FaceTime to no longer work on both my Mac and now iPhone!

We are all Apple users, like yourself, in the community, so Apple is unlikely to see your "Fix it" request here.

Wondering what "no longer work" means really ...

eg: can't log in to FaceTime and Messages / error message that points to the cause ? / apps "crash" or freeze ?

• Restarting your Mac and iPhone may be worth a try, as that may re-establish the connection.

• You can check for an outage: (a green dot means all is ok) Apple - Support - System Status

• Apple support have a trouble-shooting article online (link below) that may help:

If you can’t turn on or sign in to iMessage or FaceTime on iPad, Mac, or Apple Vision Pro - Apple Support

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If you still need help:

MacOS 26 and iOS 26 are major upgrades, and much re-indexing and more may continue for some time after the upgrade, using memory, storage space etc., for a time.

Other possible causes:

• interference from VPN or third-party apps (like unneccesary virus checkers ad-blockers, cleaners etc)

(try turning them off, see if that makes a difference. If you wish: use uninstallers from their developers)

• Any necessary third-party apps need to be kept up-to-date for compatibility, so they don't cause issues.

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If you want to send feedback to reach those who work on the software behind-the-scenes at Apple:

There's a feedback website: Product Feedback - Apple