Hello,
Until I or someone else can troubleshoot this, can you try the older version of the game build - demonheart-windows-x32.zip - older version 1.65? It should run on 64 bit as well. Sometimes the new engine is incompatible with someone's hardware, but hopefully at least one build works.
Viewing post in Since the latest update, game crashes when I try to launch it
@Rolling Crown - this appears to be an issue with itch's launcher. I used the 'manage' option to open the folder where the application was saved, and double clicked the demonheart.exe, and the game opened just fine. I have had a similar issue and solution with LustDoll, and WolfQuest's recent patch has reported the same issue, so I don't think it's a Demonheart issue as much as it is a Itch.io issue