"I appears that I was able to download them all,"
Download, or install from disk ?
If you have downloaded and installed the game from a site such as Good old Games include more details about
what is, or is not happening. If you installed from disk read on....
If you installed the games from disk there may be an issue with DRM Blocking.
A malware developed by MS that prevents hundreds of disk based games from launching.
This should only apply to later versions of Myst. Version 1 & 2, and possibly Riven, only use the old CD check
type copy protection, but the newer versions use either SecuROM or SafeDisk copy protection,
both of which are being blocked by MS. I have more details regarding DRM Blocking in my rant ---here---
- With Win10 the only way to circumvent DRM Blocking is to use a noCD fix/hack, or submit to MS's extortion
and buy the game from an online 'dealer' . The complete series will set you back $30- , possibly half that
if you wait for one of GOG's frequent sales.
https://www.gog.com/game/myst_masterpiece_edition
.