On my iPad 2018 I erased contents and reinstalled a fresh copy of iOS 12.1 To my surprise, iCloud key chain had to be manually turned on and consequently 30 of my passwords have not been carried over - lost. Also, Mail had to manually be turned on but its the loss of the passwords which has caused havoc. Has anyone else had that problem with loosing your keychain passwords after a fresh install? Is there a solution? Thanks for your interest.