@marwin74 Passphrase or password? They are not the same thing.
If you have change your Opera account password recently, the Sync may ask for the old one because your saved passwords were encrypted and stored using that old password and Sync/Opera needs it to be able to get the passwords.
If you haven't changed your account password, logging in to Sync is enough to get your saved passwords.
Now, if a passphrase have been set up, then you will also need to inform it. And the only way to remove the passphrase is by deleting the synced data.