Cannot login to iCloud on iMac Pro
I have an iMac and several other devices. Only problem is with the iMac where System preferences is inviting me to Sign in to my Apple ID. When I do, I get told that I am already signed in to iCloud and to delete my ID from internet Accounts and sign in again. I have done that but I am going round in circles. My other devices (MBP, iPhone and iPad) all work fine. I can log in to iCloud through Safari and it shows that my iMac is a connected device. However, I cannot get beyond the login screens. It sounds like something has corrupted somewhere. Anyone any ideas?
iMac Line (2012 and Later)