I found a few possible fixes, can you give these a try?
1. Try to launch the game directly from the shortcut or the app file, and not from the itch app.
2. Make sure you have access privileges to the drive/folder the game is installed on. (for example, if playing on a guest account, you may not have the necessary permission to write to the folder)
3. Make sure you're not running the game in sandbox mode
If none of these work, or aren't applicable to your situation, then I'll dig more into it tomorrow.
I'm glad to hear you're enjoying it. :)