From pinned discussion thread:
What should I do if the update seems to stall or stop downloading?
The first thing to try is closing down MSFS and restarting it. The downloading should start again once MSFS is restarted. If there are problems with a particular file downloading repeatedly (on a loop) then exit MSFS and browse to the download location where the file is downloading to using windows explorer. Delete the offending file (if it is listed) or the latest downloaded file in that folder and then restart MSFS. The patch should continue as normal. (Note only delete files do not delete folders!)