Yeah in the reviews section many seem to complain about having various problems in Windows 7 (or 8.1), the symptoms seem to be different though (for some it doesn't even launch, some have some problems during the gameplay etc.). Maybe I should try it too whether it works for me.
It may be GOG support has been instructed to first go through certain steps with the customer before giving the refund, so please be patient with them, instead of going "I've already tried everything you could think of so just give me my refund, dammit"...
There seem to be some success stories about getting it to work, but yeah it does sound quite finicky.
https://www.gog.com/forum/myst_series/myst_masterpc_on_win7_64_what_worked_for_me_and_thoughts https://www.gog.com/forum/myst_series/myst_masterpiece_edition_and_windows_10_quicktime_issues_as_always Damn Apple with their Quicktime, giving nothing but problems on modern PCs! I've also had Quicktime problems with e.g. Wheel of Time game (not on GOG, I have a retail version). I start feeling Apple released Quicktime for PC/Windows in order to cause trouble there, so that people would jump ship to Macs...