Not supported on this architecture

[Vroqren]

I recently re-downloaded my Book II game, to update it to the newest version, in order to try Fathermurk. The icon in it's folder has a cross on it, and when I try to open it it says that it "couldn't open because it's not supported on this architecture." Any ideas?
I'd really appreciate any help I could get. I haven't deleted my old copy yet, but I don't think that's the problem.
Here's a screenshot of my Book II folder.

[Vroqren]

Well. There's my problem. Alright, I guess I will not be trying out the Fathermurk caves. It was worth a shot, but all this time and energy (I had to click at least 20 times.) is of no use. Thanks for the info.

[SpottedShroom]

What are you doing when you see that error message? What version of macOS are you running?