Keychain not working on OS X Catalina, working fine everywhere else

I have recently done a fresh install on my Mac mini 6,1 using Internet recovery. Initially it installed Mountain Lion, but then I found out how to install Catalina from Internet recovery (VERY useful - Thankyou Apple). Everything seems to be working fine apart from Keychain.

I click on Safari>Preferences>Passwords> enter password and its completely empty.

I have been to System Preferences>iCloud and Keychain was ticked. In an attempt to turn it off and on again, I unticked it and was told any device running iOS8 and earlier or OS X Yosemite, iCloud Keychain would be turned off on those devices also. No Problem, I don't have any devices running that software. Click continue, Enter iCloud password. Done.

Keychain check box is unticked, for about 10 seconds, then, automagically, it is reticked.

Keychain password list in Safari is still blank.

Keychain passwords on my iPad and iPhone still populated and working perfectly.

Please tell me I don't have to do yet another fresh install.

Please help.

Thankyou.