Can't log into iCloud: Verification Failed - Your username or password is incorrect.

You could try applying a fix that worked for other iCloud account related issues back in DP1: Simply deleting the files in the following folder:

~/Library/Application Support/iCloud/Accounts (that's not the library folder in the root directory, as I'm guessing you're aware)

I am. 🙂

This does not help, I already deleted the whole Accounts folder. Sorry for not mentioning it.

Already tried that as well. Looked the same like the normal upgrade but without the hoped-for wizard. 🙂

There's a second interesting file in that /var/db folder:

.AppleDiagnosticsSetupDone

Also 0 bytes, so another present-or-not file like .AppleSetupDone

Rather you than me though 😁

Actually, now that I come to think of it, the wizard-lite struck me as unusual - I'm not sure that it is normal for every update. It might be that the firmware update changed something that prompted OS X to confirm that it was still on the same computer and not just cloned someplace else. Maybe reapplying the firmware update would do the trick?

When deleting the .AppleDiagnosticsSetupDone the system is performing a hardware check. It's nice when you assuming faulty hardware.

Well that figures I guess. Good to know.

Out of ideas for now though... 😟

It did not. 😀

I applied both the firmware and the system upgrade packages as I was reapplying the upgrade. But of course it could be that he noticed that the firmware didn't change. However I hope that this wizard will come up again. I would hate to reinstall and reconfigure 10.11. 😐

Alright. Thank you for your valuable time and precious hints, friend. 🙂

A further thought: Have you tried logging in to iCloud.com on a browser and looking at Settings > My Devices > The Offending Computer > Remove Device.

Of course you may not see your computer logged in, but it would be interesting if it actually was. It would confirm your username and password works elsewhere.

Yes, already tried that as well. My Mac is listed there because for some works I still boot into Yosemite. I removed the device again and it keeps out there as long as I use El Capitan. My iPhone and iPad are still listed there. So:

Username and password works under: iPhone, iPad, Yosemite, iCloud.com. It does not work for El Capitan. It's clearly a El Capitan bug.

Worth a shot :]

I've read and/or tried to troubleshoot dozens of iCloud account related issues with 10.11 and yours seems the strangest to me - all others could be explained/resolved without assuming a bug that either doesn't correctly read/decrypt username & password from server or fails to check them against input properly. Bizarre!

User wOlf from MacRumors brought the file ~/Library/Preferences/com.apple.SetupAssistant.plist to my attention.

It contains a key "DidSeeCloudSetup" with a value "true". So the "setup wizard light" is called "cloud setup". (Or should I be sceptical because it is not called icloud setup?)

However, I played with the booleans of this file, none of them has an effect in my case... :/

Thanks for reporting on it anyway - that's interesting.

I just tried logging out of iCloud, rebooting and, from Finder, running the Setup Assistant app (/System/Library/CoreServices/Setup Assistant.app).

It prompted me to login to my iCloud account with a username and password, much like after the first boot of the update. It changed nothing else - didn't even close down any other apps. It contains an executable called "minilauncher", reference to which is contained in a compiled (i.e. gobbledigook) file close to the string "firstbootiCloudlogin"...

So, you never know...