I am still downloading the whole thing - extremely annoying especially because I couldn’t even get a new install past the initial screen. Tried everything -removing all traces inc in registry of MSFS and still nothing. So now after hours of trying over 3 days I found the culprit. My windows X-box app had been updated (quietly and in the background like all updates) and my gamertag ID was corrupted.
I discovered that by chance because I tried logging out, restart PC and logging in. So the absence of any troubleshooting tool or even a quick error message made me reinstall unnecessarily (again). That is all that was stopping it. (And I really wish they had made a pure PC version and a seperate X-Box version).