Hi Daniel. When you change your Firefox Account password, your Firefox Sync data gets deleted from the Mozilla servers. This is a technical limitation with how encryption works. The previous sync data is encrypted using whatever your account password was at the time. If the account password changes, it no longer matches the password that was used to encrypt the data, so that data can no longer be read. If you sign into Firefox Sync again on Firefox, new data will get synced, but you can't recover any existing bookmarks or other information that was stored on Firefox Sync and not already saved to a browser.