find it in safari/preferences/autofill
edit: It works if you do it on your iOS device.
SOLVED!!
Don't know what the glitch is but if you login from your iOS, it saves to iCloud Keychain and works from your mac!
Many thanks rikscha!
What I did was to put in my login and password, but I did NOT login - instead I refreshed the page and then it worked.
Still a problem. On the change password screen iCloud keychain suggests a password but doesn't save it.