First did you set a sync to any device? Also firefox sync isn't to be used as a backup device it only mainly sync between devices and back. And sometimes it restore some or most of it if the sync was correctly set. But if there is no other devices sync the chances don't look good for it the sync to restore if it can back.

Hello,

Thank you for reaching out to us. I understand that you have recently performed a clean installation of Windows and reinstalled Firefox, but your sync data seems to be lost. I'm here to help!

When you perform a clean installation of the operating system, it can sometimes disrupt the synchronization of your Firefox data. However, there are steps you can take to restore your sync data:

Ensure that you are using the same Firefox account: Make sure you are logged in to the same Firefox account that was previously used for syncing your data.

Check your sync settings: Open Firefox and go to the menu (three horizontal lines) in the top-right corner. Click on "Options" or "Preferences" (depending on your Firefox version), then select "Firefox Account" or "Sync." Verify that the data types you want to sync are enabled.

Force a sync: In the same "Firefox Account" or "Sync" settings, you can try clicking on the "Sync Now" button to force a synchronization. This should initiate the sync process and retrieve your data from the server.

If these steps don't resolve the issue, you can try disconnecting and reconnecting your Firefox account to trigger a fresh sync. To do this, go to the "Firefox Account" or "Sync" settings, and choose the option to disconnect your account. Then, sign in again using your Firefox account credentials.

Please note that in some cases, if the data was not properly backed up before the clean installation, it may not be recoverable. However, I recommend trying the above steps to see if it helps restore your sync data.

If you have any further questions or need additional assistance, feel free to ask. I'm here to support you.

Best regards, Firefox Support Volunteer