Another thing you can try is to goto the URL opera://about, take note of the "profile" path, goto opera://settings/syncSetup, set "Do not sync data", goto https://www.sync.opera.com/ again and reset your passphrase if there's data there, click the icon at the right of the address bar for Sync, and click the little logout button, close Opera, and delete the "Sync Data" folder in the profile folder. Then, when you start Opera, you can set up sync like you did the very first time you used it.