I have a Garmin Fenix 3hr. I have not been able to connect to the express app in quite some time. The app shows in blue "new device found" but it does not ever connect to the watch. I have cleaned the connection and bought a new cord to no avail.
You should probably post this here to get better response - https://forums.garmin.com/apps-software/mac-windows-software/f/garmin-express-windows