Can't Log Into iCloud Since Catalina Upgrade

Been reading the thread on this. I had the same issue when I installed Catalina from El Capitan - couldn't log into icloud or get my icloud email to load. It kept complaining about my id already being signed in. I finally fixed it last night. Initially I tried reinstalling Catalina but that messed up my APFS and I got the "Could not create a Preboot Volume for APFS Install. I researched that and apparently somewhere around Sierra Apple changed from HFS+ to APFS. Everything I found was saying I should delete the hard drive but I wasn't comfortable doing that. Figured that by now Apple had figured out how to roll that into the upgrade install so I opted for fixing the volumes on the drive. Then I reinstalled the Catalina OS. After that completed I hoped my issue with my id would be resolved but it wasn't. It was still complaining about the account I was using (my appleid) was already active. I stumbled upon someone (I'm going to go back and try to find their handle to give them credit) that said you should :

0pen the Terminal app

Type defaults delete MobileMeAccounts

Hit enter to execute this command. This will force macOS to sign you out of iCloud - now you should be able to log in from the iCloud pane in System Preferences.   

When I did this I got a message that the default shell had been changed and it prompted me to change it to the "zsh shell" which I did and then proceeded with the above.  The prompt came back and said that a MobileMeAccount didn't exist. Regardless, it did FIX THE PROBLEM!

Hope it works for you.

Thank you for responding. I kept trying different things, most to no avail.

I ended up trying a clean install twice. This is what happened:

1. When installation was finished and MacOS wen to recreate everything from Time Machine, it took eons. System reported 12 MB/s transfer speeds. Once done, I was back to square one, unable to connect to Apple ID servers. Rebooted and then my MBP would connect to wi-fi, but there were would be no internet connection. No amount of fiddling with DNS settings, firewall, etc. worked.
2. When I did the second install, I opted to transfer everything from a bootable HD (a CCC clone of my drive). The process went a lot faster. When finished I got a lot of error messages about various library files. Most messages repeated themselves 10+ times, as if macOS Catalina were trying to resemble Windows Me or Vista. Wi-fi only worked after a reboot. Now everything is working smoothly, except for a small glitch in Photos (some pics that were always on iCloud are now downloaded and in the list of "Unable to Upload".

This is happening to me too. Happened on the iPad too. Kept asking me to verify credentials. On the iPad logging out and back in fixed the issue. I logged out in Catalina and it won't log back in. Keeps spinning. I read with the iPad update the servers were overloaded, so guessing it is the same here. Hoping by morning I can log back in.

Open Finder. Hold the Option key. Click Library. Find your Keychain folder. Copy the content somewhere "safe" on your HD/SSD. Reboot your Mac. Log in to your Mac Account. Go through some gyrations when prompted to sign back into iCloud. Voila! Your keychain will be restored.

NB: don't be too impatient and realize that Keychain, as a web service, needs to download your "stuffs" from the web and write them to your Mac. In other words, give it some time to synchronize.

When I first did this, I got an error too. In fact, it was a very crude, old looking and unpolished dialog. Something you’d imagine that Apple doesn’t use much any longer. It had a red symbol on it. I pressed on and eventually go through.

At least you kept your original files. If you are unable to press on and the occur keeps occurring, try and restore your keychain files and reboot again. Then setup an Apple Support call.

To me it’s unfortunate that this piece of critical functionality for iCloud is seemingly so fragile.

This worked for me after trying everything else, found it as a fix for something else

System Preferences > Network > and create a new Network Location (normally its says Automatic) and to re-join a known working wi-fi network.

Then log on to iCloud and follow instructions

(before this I had logged out of iCloud and restarted MacBook)

So I've been reading through all the responses. I was looking for one that seemed the best option. I tried a few but to no success. I finally had enough and clicked the "Sign Out" button at the bottom of the dialogue box. It prompted a new dialogue box asking if I wanted to save a copy of stuff like Calendar, News, etc. I clicked yes and it prompted me that iCould needed to download 2 updates before it could sign out. I allowed the downloads and it prompted my password to log out of "Find My" features. Once I did that it took me to a new login screen. This time when I logged in it prompted security passcodes along with the password. It worked this time for the login. So maybe try to log out and save copies to prompt whatever download that was missing for the login to work. Good luck.

I dunno if it's me but this make little sense (to me). When opening the finder the Library isn't readily available and to my knowledge most people don't know how to find it. Also what is considered a "safe" place to copy the Keychain folder to? Gyrations to sign back in (like a Dancin' Fool - FZ '79) I have no idea what is meant by this once prompted (to sign back in). Can you please simplify this for this half-wit? Going nuts not being able to get back into the cloud... P.S. I don't understand why Apple continues to put out broken or stuff that should be tested more before releasing it to the public... for all the money spent on these devices they should have a bit more respect for the consumer! Shame on you Apple!

Brilliant! I had the same thing (I had to change my iCloud password as someone was trying to log in in another country). Same thing happened, couldn't log into iCloud, all my email accounts were failing to login on the Mail app. I was on apple chat, for 35 minutes. Then on the phone with support, with three reps, escalated to senior rep. He said there were multiple tickets for the same problem, he still couldn't figure it out. I was going to wait for the next update or do a fresh reinstall until I came here! 5 minute fix, going into terminal app and typing that command. All done! Thank you so much for posting and thanks to the OP.

Responding to suggestions how to back up the Keychains folder content... How will the OS know where I copied the keychains ?

Shall the original Keychains folder remain in place ? I made a copy folder side by side "Keychains2"....would that be to any benefit ?

In my case there is no iCloud icon showing up in the Control Panel.

I go into the Control Panel, under Accounts I find iCloud.

I try to login with my userid/password (which works to login to the Apple ID site from a browser)

and get "Verification Failed . An unknown error occurred"

I tried creating a second userid, log into that one and I can login to my iCloud account from there.

But then under that account I won't have all the files and work material of my regular account so I want

this to work on my regular account... Suggestions ? How does it work; can two macbook users use the same iCloud account or need I somehow be sure to remove all relations to this iCloud account from that new macbook test user account I created before any chance exist that I can again use this iCloud account with my desired regular account ?

Same if I try to login to iBooks, I get the "An unknown error occurred".

An observation is that if I type an incorrect password the dialog notices this and complains.

So the Unknown error prompt appears after submitting the correct password.

I signed-in in "iCloud"... not under "Overview" and it worked... works for you?

Mine is ok but I noticed I had to turn Keychain back on and sign into iBooks. I’ve not gone through everything yet.

yes