Well if it is only post update then it is one of three things

1) You're wrong and you've put in the wrong login details (possible but knowing you unlikely).

2) They've changed something on the iCloud platform itself which is only used by the latest MacOS and has a bug, but then I would expect it to be more commonly reported. It's almost certain that they changed / added / extended an interface between iCloud and the latest MacOS because of the Chat with Businesses feature in Messages.

3) Could be update related because the luxury that Apple has (and why it's OS is so much smoother than Windows) is that it knows precisely which hardware it will run on and as a result does put in code specific to particular hardware versions.

4) Something went wrong with the two-factor authentication if you have it turned on. That's proper w**k anyway - for example when I use two factor on my iMac, the message with the authentication code is also sent to my iMac so that's a bit of a waste of time.

Some ideas here though as I think iCloud login issues can happen every time there is an update.

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Posted By: Steve in Holland, Apr 10, 14:46:59