I think that you should have made the secondary email your primary email when you still had access to the primary email address. I assume that you now get a warning that you need to use the primary email to make the change from secondary to primary and can't use the secondary email address ? If you aren't able to use the secondary email address to get access to the account then you will have to create a new Firefox Account with a third email address. *https://support.mozilla.org/en-US/kb/ive-lost-my-firefox-sync-account-information