There can be several reasons why Mi Smart Share isn't working on your Windows after a fresh install. In most cases, it could be due to running an older version of Mi Smart Share. Let the app update itself automatically in the background and then retry sharing files. (Latest version of Mi Smart Share at the time of writing this article: V1.0.0.452) If you use any VPN service on either of the devices, you will have to turn it off before sending/receiving any file.