same problem...tried to manually remove the Account (/Users/<username>/Library/Application Support/iCloud/Accounts) with no luck. Reboot did not work either.
Hey Guys! I've finally managed to get it back working with a little workaround!
I'm now successfully back connected to my iCloud account on macOS Sierra...
Here's what i did:
First i followed this discussion and get the thoughts on what's the problem here (It's the KeyChain!!)
But as on this discussion it wasn't mentioned how the guy from the "Genius Bar" fixed it. I've searched for how to RESET the keychain and then found this:
So i only followed the tutorial on ccm.net and rebooted my mac. Then i tried it again to login to my icloud and....
HEY! It worked again!
Then, just set up your settings again and you're back to the game... Also if you've shared/saved your keychain to iCloud before, the new created one will get back all your keychain items from iCloud right after! ;-)
So that's it....
Happy testing the new betas and best regards!
i already have the solution but needs to be "currently being moderated" whyever. So wait a bit for long description...
Short one here:
1. open Keychain.
2. go to "Keychain settings".
3. click on "general" and then on "reset keychain" and type your password.
4. reboot your mac
5. sign in again through icloud settings. now it should work!
If you've saved your keychain to icloud before all your items will be getting restored successfully.
This does not work for me.
Found a solution that worked for my setup - opening Network Preferences and disabling the proxy, which was set to Automatic Proxy Configuration with an academic proxy URL. The specific proxy config I was using kicks in only for academic URLs (journals, etc.) and should not affect apple.com connections, but maybe there is a bug somewhere in Sierra that causes this issue when a proxy is configured.
doesn't work for me either - but i get to reset all my two auths now!
THe only thing that worked for me, was to re-install 10.12 over the existing 10.12 installation. That finally got me through the iCloud setup process and everything is working like a charm, now. I only had problem on one of three machines, weird bug though.
update: i tried the keychain several times...several. It finally worked.
Same problem here but with the workarond from arnoldo83 i was able again to login to my Icloud.
Many thanks arnaldo.
Keychain Access application Keychain Access -> Preferences. Click Reset My Default Keychain and reboot. Worked fine .
I tried you solution but when I tried to log back in on my Imac I kept getting sent back to the log in screen. To get back into my Imac I needed to log in as a guest and change my password in preferences.
Am I missing a step here?
Now that I have reset Keychain all my logins have disappeared and I cannot get them back from the cloud as I cannot log in.
For some reason I am able to log into Icloud on the web but not on my Imac.
Any ideas or thoughts
reset keychain password didn't solve problem at my case, but some privilegues problems seems to appear in /Users/Shared, causing to not allow iCloud login, on cranked system only.. This article solved my problem, now I'm able login to iCloud normally as ussual - https://apple.stackexchange.com/questions/235957/after-el-capitan-update-i-cannot-sign-in-to-anything-with-my-apple-id-this-a
Hopes it helps you