I updated to OS X El Capitan and lost all my groups in contacts. I have been on the phone with Apple Support for 3 hours and can't restore the list of groups in my contacts. Can anyone help?
Open Contacts (your address book) select Preferences in the top left tool bar of your screen - go to Accounts and check the box for Enable This Account for the iCloud Card DAV on the left side of the accounts window. Your contacts and groups should all appear. Do a search for your groups in the address book if they don't automatically appear - worked for me. Good luck
This answer would only be helpful if no contacts would be synced. But this is not what was reported originally. The groups are missing, not all contacts. Only then does it help to make sure that the account is enabled.
I have the same problem now, where all contacts sync fine, but the groups do not and I have more than hundred groups and more than 3100 contacts. Going to the iCloud account via browser I can see that all is fine, on my iOS devices (iOS 10.3.3), all groups are shown fine. Only on my 2nd El Capitan Mac OS X 10.11.6 the groups do not show up, only the contacts. I have disabled/enabled the account, I have signed out and allowed that process to delete all contacts and other data on the Mac, and I have even gone to drastic measures such as deleting all AddressBook support folders in the Library, allowing the systems to rebuild them from scratch after reboots and doing this all in safe mode. All to no avail. The groups do not sync to my El Capitan Mac.