"You can’t sign in at this time" when signing into iCloud I recently upgraded my fairly new MacBook Pro to OS X 10.11 (El Capitan). I started the Notes app, hoping to see my notes, but they weren't there. I clicked on iCloud in the Settings app and typed my Apple ID and password, and a dialog box showed saying "You can’t sign in at this time. Try signing in again.".

I am sure I am typing the right Apple ID and password because I can log in from my phone, and I can log in from the iCloud website.

I tried deleting my ~/Library/Application Support/iCloud/Accounts directory as described here and that didn't seem to do anything.

I tried the procedure described here and that didn't work either.

Why is this happening? What can be done about it?
I called Apple Support. We tried several things. Eventually, I started Keychain Access, and under the "Keychain Access" menu, clicked "Preferences". In the Preferences, I clicked the "Reset My Default Keychain" button. I had to re-enter my Mac and iCloud passwords. Everything appears to be working fine now.