I've been experiencing exactly the same problem for the past month or so on my Macbook Pro. I never used to have a problem exporting, now regardless of the settings, all I get is a black screen with audio. The preview and rendering are fine. I've tried many of the "solutions" posted online and nothing changes the end result.
Interestingly, I just tried importing the black video into Resolve and it plays fine. The issue is obviously related to Quicktime, despite the fact that the exported media was in Quicktime!
Any suggestions would be appreciated. See my settings attached, although I have tried many including NTSC with the same results.