I've called the big guys to help you. Good luck.

hi aspmajaa, first you'll have to try resetting your account password at https://account.services.mozilla.com/forgot - enter the mail-address you've used to sign up for old sync originally in the username field and follow up with the password reset procedure through the mail you'll receive. firefox 29 and above use a new sync login system which isn't compatible with the old username/password/sync-key method anymore. you could try this "hack" to get a new firefox version to connect to the old sync account though once you have a working username/password again: enter '''about:config''' into the firefox address bar (confirm the info message in case it shows up), right-click somewhere in that page & create a new string preference named '''services.sync.username''' with a value like '''fake'''. afterwards you should be able to connect to the old account through the firefox options > sync panel. click on '''set up firefox sync''' > '''i have an account''' > '''i don't have the device with me''' where you can enter your credentials. if this worked and you could import your data successfully, please migrate to the new sync afterwards: [[How to update to the new Firefox Sync]]