I googled this issue to death, nothing worked. All the advice from all the experts was ridiculous. The only thing that worked for me was reverting back to an older version: ver 2.3.18.0
I know many wont like to do this, but its the only way I can get garmin express installed and update my maps.
I tried all the 4.x.x.x and 3.x.x.x versions and got the same error. ONLY version 2.3.18.0 worked.
Im using Win 10 x64 on a HP laptop.
You have to google for it.