Problems with building Mac version via Windows

I seem to be having, or rather - a friend is having problems - with loading up my prototype via his Mac. I built a Mac version on my Windows PC, but he gets an error saying 'the application can't be opened'. He can't see any executable file either.

 

We'll need more to go on. Macs don't normally see "executable files," we see application bundles, which look just like other files except that in the Get Info window it will say "Kind: Application" (and if he shows file extensions, it will be .app — but most Mac users have file extensions hidden).

Also, the error certainly does not say "the application can't be opened." It includes details, and those details contain important clues as to what is actually happening.

If you can't get to a Mac yourself, then I suggest you ask for a screenshot.