Yeah, there are a couple of similar, minor points on MAC, that you just have to work through a bit.
Make sure that BFD has permissions to your Documents and your Removable Volumes. That’s an old one, but it bears repeating.
It’s better if you add and scan the path to each expansion separately, instead of searching an entire drive. I found it got bogged down and got stuck on a few if I did them all at once, but got through them all just fine when I added them individually.
If you have some libraries that have become unlicensed in the process (I’m looking at you, BFD2), make sure they’re unchecked from your Content Locations, or you’ll re-open to the content location page every time.
Also, BFD3 is more sensitive to multiple Volumes with the same name than before. I have a backup FXpansion drive that I often have online, and I now have to eject it. I think this is really a Mac OS issue, because the same issue just cropped up in ProTools recently.