Received my 920xt last Monday and am very happy with it. However....
Garmin express would not recognize it (was showing as a drive in explorer) - I'd been having problems recently with my 910xt being found also.
Spent 2 hrs with Garmin support by phone - all to no avail, so was disappointed not to be able to set up a wireless connection (I had been able to link via Bluetooth to my iPhone 6).
Anyways over the last three days, I have uninstalled express numerous times, checked my .Net via windows and read as much here as I could. Finally this morning I was successful, here's what I did.
1. Uninstalled Express and Virb Edit, also removed Garmin Updater (though I think it was taken out by removing Express).
2. Searched entire computer for GarminDevice.xml - found several copies and numerous different locations, included one on the 920 itself - delete all.
3. Searched entire computer for Garmi.* - reviewed & delete everything, folders, short cuts, password files - it all went.
4. Emptied trash folder and restarted computer (with 920xt disconnected).
5. Checked .net via link found in this forum.
6. Repeated steps 3 & 4
7. Downloaded fresh express file (had deleted in step 3).
8. Opened express and plugged in 920 and success........
9. Downloaded and installed fresh virb edit, plugged in Virb Elite and it was found also (still have an existing sync issue with the camera!)
Anyhow, the above is all very simple and was as thorough as I know how, it took me three days of failed attempts to get to this point, hope this helps anyone else having the same problem.
Happy thanksgiving, Glen