iCloud Keychain refuses to setup on Catalina
If you see an error like this and cannot continue, one easy fix is to sign out of iCloud and then sign back in.



I'm still perplexed and not sure what ithe dialog wants to Upgrade since my password contains all the correct characters and I already have had two-factor auth on my account since it came out. :D

Also, if the date / time is off, you might check that if you get iCloud errors or can't sign back in once you sign out.