If you reset your Firefox Account password without using the recovery key for your account, any data that was stored on Firefox Sync is no longer accessible. This is because that information is encrypted using your account password. When your account password changes, it no longer matches the password needed to decrypt the information from the Firefox Sync server. There is a warning about this when you go through the password reset process. The one positive thing is that what happens to your Firefox Sync data won't impact data that's already on your computer. So, whatever device you were using Firefox on should still have those usernames and passwords saved on it. If you log back into Firefox Sync, that existing data should get sent back to the Firefox Sync servers and then be transmitted to other connected devices. If you don't have that data on a copy of Firefox on any of your devices, your only chance to get that data back is if you created a local back up of your Firefox profile folder, you have a folder called '''Old Firefox Data''' on your desktop or you used the Windows 10 reset tool to reset your computer. Unfortunately, if you don't have a back up of the information or a device that's capable of accessing that information, you are out of luck. Hopefully this post is able to help you.