Hi Aeon13.

What and how many devices have you set up for Sync? Do you use the same account for all of them?

Also please read Firefox Sync troubleshooting and tips.

I'm using only one PC and one firefox account. When i did reinstall Windows, i tried do sync and it doesn't work.

So you logged in to the account used before the reinstallation to recover the old Firefox data? Did you know the password, or recovered it before signing to the account in the new installation?

Sorry, but Sync wasn't intended to be used as a backup medium. It's purpose is to synchronize data between multiple devices.

It does work when reinstalling the operating system, but some users who have a problem when using it in that manner make the mistake of resetting their Sync Password [see the screenshot below], which wipes the data on the Sync server. There is a warning message that all data will be wiped, but it seems that too many users have proceeded with changing their Password anyways, ignoring that warning message - or not reading and understanding it. The Password is used to encrypt data as it is sent to the Sync server; and then used to decrypt that data as it arrives on another (or the same) device. That data is worthless without the original Password that it was encrypted under.

the-edmeister thank you, i guess i didn't pay attention...