I tried to open an existing project and created a new one. Both worked fine.
With the OS X Beta 5 and 4.8.3 it did not even work to open an existing project which worked for some users.
That’s great news. Maybe it’s time to risk it. 
3 Years after the initial post released, Im here, running on still, wondering “WHY THIS STUPID ENGINE INSN’T WORKING!!!”, and it seems like just isn’t a stable OS?? Maybe?? Anyway, I can’t upgrade, I’m stuck here on the good ol’ El Cap wanting to try out both Unity and UE4 but only one works. I don’t want say which as it may upset the developers, but I think you can guess (Hint: It ends in 4!). Oh well. I can deal with the one that IS working, ya know? Any way, good bye!
P.S. If you ARE reading this 3 years after this post was released, check out my YouTube, will you? It’s . Thanks for the support!