If you want sync don't add any "sync" line in the config file!!! Adding that will disable it!

Contacts must have at least area code + phone number in your address book.

@kurtyy: That string is not used in the registration process but in the login. Now Whatsapp is verifying the token, which was totally ignored before. We'd need to hack how the token is built, since it derives from the phone number and other data... and that's not easy.