Took me awhile to find this out.
1. Create an Account in Address Book 5 with CardDav Setting
It doesn’t really matter what you entered, we are going to change from Configuration.plist
2. Close Address (Apple Key + Q)
3. Open Terminal
4. cd Library/Application\ Support/AddressBook/Sources
5. ls -l (search for the latest updated directory)
6. cd [the directory name]
7. nano Configuration.plist
8. Ctrl + W (Search) servername
9. Change the servername <string> by entering this format
<string>https://pxx-contacts.icloud.com:443/xxxx your icloud id xxxxxx/principal </string>
10.Change username <string>
11. Ctrl + X and Save
12. Open Address Book, iCloud should be Syncing!
How to find my iCloud Unique ID?
Please have a look here!