S4S Can't locate Blender

I've downloaded both Blender (both 2.7 and 2.78) and S4S to get around the error but every time I try to export any mesh I get a message saying "The Sims 4 Studio was unable to locate your Blender installation. Would you like to download it now?". Clicking 'OK' takes me to a download link for Blender but, like I said, I've already downloaded it (countless times!!).

I'm on a Mac so maybe that's the problem but I'm not sure. Sorry if this seems like such a simple problem but I'm a beginner and I've no clue on how to solve this.