Nov 13th I upgraded to High Sierra. During the boot proces the password for iCloud is asked (I think I entered it correctly). However a spinner started spinning (basically forever). So I shutdown the Mac (button back) and rebooted. Systems works okay. Except for iCloud.
Update: I managed to delete my previous accounts towards iCloud. However I'm not able to connect/recreate accounts again.
iCloud asks for UID/PW and after that a never stopping spinner occurs. No difference for wrong UID or Password.
I checked the UID/PW for correctness using different devices/websites. Also tried other AppleId's.
What can I do to get this working again?