OK... for others that might have run into the same problem, the cause has been found.
On the MacBook, I went into the KeyChain and searched for all keychain entries related to Opera. Then deleted them.
You must reboot your system. Then go in and re-login to the sync server within the Opera app.
That fixed the issue, but after many reinstalls I really think there should be some option for a reset within the Opera App itself. Good thing is it finally worked.