After many trials, tribulations and reinstalls it is now clear that the basic problem is that the fresh install download stops at a bit over one GB. I've tried using both Microsoft Store and the XBox app. In the XBox App, the download shows 152 GB at first. But it always completes at about 1 GB. I've tried both wireless and Ethernet. Windows 1909 is up to date. I've made sure all MSFS related files are removed after each uninstall. I cannot install on C drive (since it has FSX on it, among other things), so I try to install on D (which has plenty of room). I succeeded with the initial installation and previous update. Does anyone have any ideas?
Thanks to pjs37 and HiFlyer for earlier help on related issues. But it is now clear that I need to be able to download the full file.