Well, I don't know if you (@GiftA-MSFT ) did something to help, but it's solved! Thanks if you did take that initiative, I appreciate it. :-)
...or it could be that after 4-5 hours the upload just completed. My internet connection was fine (it's a 40Mb line), so I'm not sure what the solution was. Perhaps patience alone is the answer.
Anyway, thanks for taking an interest in my problem either way.
Best wishes. :-)