Well, Yahoo finally replied back and suggested these steps. I have gone over each step and unfortunately it does not work. I get a pop up error message claiming that SSL / Authentication failed. I have tried without the https, and still the same issue. I have replied back to their support team asking for a new solution.
If you guys want to try it out - go ahead and please report back if it works for you.
Thanks! 😉
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After reading your email, I gather that you are encountering an issue
with syncing between your Yahoo! Address Book and iPhone not working as
it previously did. I understand this could be frustrating, and apologize
for any inconvenience caused.
If you recently upgraded the operating system on your iPhone such as
with the recent release of iOS 5 software for the Apple iDevice, that
could be the cause of the problem.
You can delete the Yahoo! CardDAV account entirely from your iPhone and
recreate it, forcing a new sync.
To remove your Yahoo! CardDAV account from your iDevice:
1. Go to your iPhone, iPad, or iPod Touch settings application
2. Tap "Mail, Contacts, Calendars"
3. Tap "Yahoo! - Contacts"
4. Tap "Delete Account", Confirm deletion by tapping "Delete Account"
once again.
To sync your account:
1. Go to your iPhone, iPad, or iPod Touch settings application
2. Tap "Mail, Contacts, Calendars"
3. Tap "Add Account"
4. Tap "Other" and then tap "Add CalDAV Account"
5. For the Server, you need to enter https://carddav.address.yahoo.com
6. Now, type in the Yahoo! user name and password you use to sign in to
your calendar
7. Once you click "Next", the iDevice will verify your user name and
password
8. The next time you open up your iDevice Contacts app, you will see
your Yahoo! Contacts merged with the rest of your contacts. Tap "Groups"
at the top left portion of the iDevice screen to choose which Contacts
group you wish to view.