Did you need to reset your Firefox Account password when trying to log into Sync after reinstalling Windows?

If so, your data would have been cleared when the new password was applied to your Firefox Account.

Were both that Win10 PC and the Android device connected to your Sync account?

If so, connecting that Android device with your new Firefox Account password should 'sync' your password data back to the Sync server; and subsequently to your Win10 computer.

1. No, I did not reset my password. I clearly remember my password for my Firefox account. I also have a Firefox browser on my android and the application for Lockwise which still both have my logins credentials.

2. Yes, both are connected on my firefox account.

and subsequently to your Win10 computer <<< this is the problem, it's not working as it's intended to. - I tried to visit about:sync-log and found an error text file named error-sync-1584666719710.txt - There is also a message somewhere at the top of the browser that says You must log in to this network before you can access the internet

Hi, It's now syncing properly. I fixed it by: •visiting about:config •setting network.captive-portal-service to false. - It's related to You must log in to this network before you can access the Internet.