If I'm not mistaken, different operating systems run slightly differently from one another. The game seems to be built for Windows, meaning that a Mac OS would not be able to run it. A way to bypass this would be to use a virtual machine. (I don't really know anything about virtual machines, but that link explains a bit about them. Use at your own discretion, I don't know how safe they are.)
I don't know about the itch pop-up stuff, might be related to the OS stuff, but I hope this helps you a little bit :)