I struggled to get a projector working with OS/X. This was entirely unexpected since I’d never had issues in the past. It always “just worked” in usual Apple fashion. I ran out of time and had to give up.

It continued to nag me, so I started digging further. And then the obvious problem hit me. I’m using Cody Krieger’s excellent gfxCardStatus utility. I had it set to force the use of the Intel GPU in order to conserve battery power. And that was the problem. OS/X requires the NVIDIA chipset in order to drive an external display. OS/X won’t use the Intel GPU to do that.

Setting gfxCardStatus to automatically switch got things working again.