Thanks for the support article. I had not seen it and it has helpful information, but it does not address the problem I am having. It describes an empty keychain as the result of the keychain being deleted on a device. I have an iPhone and MacBook Pro. The keychain will be fine until one day it is empty when I boot and login. I have not changed any of the settings. The keychain is unchecked in iCloud preferences and in Keychain access it is empty. Doing repair does nothing.
I have to use Linc's steps to restore the iCloud keychain. I can figure out why it suddenly is empty. I have synched the passwords-login and keychain.