Hi, I guess something was added to Sync (as I do not know) that when you format that it is now gone. I believe the proper way to manage the account is to log in, turn it off, then format. I need to do that with Norton Accounts so suspect works about the same. Always :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

This is all I have on Sync :

• https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer
• https://support.mozilla.org/en-US/products/firefox/sync
• https://support.mozilla.org/en-US/kb/how-do-i-choose-what-types-information-sync-firefox
• https://support.mozilla.org/en-US/kb/firefox-sync-troubleshooting-and-tips
• https://support.mozilla.org/en-US/kb/change-primary-email-address-firefox-accounts

Please let us know if this solved your issue or if need further assistance.

I have turned it off and on many times. I guess I would have to contact Mozilla direct for this problem. I use to restore my contacts from the serve without a problem in the past.

Faora said

I have turned it off and on many times. I guess I would have to contact Mozilla direct for this problem. I use to restore my contacts from the serve without a problem in the past.

Hi, guess so. https://support.mozilla.org/en-US/kb/forum-response-firefox-sync-verification-email-faq

Bottom of that URL is the contact info for bugzilla. May even have to use a new email address.

Did you try logging in from one of the devices that are on the list and try adding the one that will not register ? I do not use it so ......