GOG.com replied to my attempt for help:
"Unfortunately, your operating system (Windows10) is not supported for this game. We weren't able to make the game work reliably on our test computers, running that system. Do you, by chance, have an older computer with an older operating system? If not, we'll credit your account."
So I guess that's it.
Well, you at least know two things now you didn't know before. GoG DID use your 1.3 patch for their version, AND Windows10 won't support MM9.
I guess it's on to "Witcher." I've played MM6 & MM7 (both on WIN10) to death.
Thanx for the prompt replies. Game on!