I know this is a pretty old question, but I ran into the same issue. And the above tips didn’t work for me. Apart from the standard checks (present in bundle, restarting XCode, the thing that fixed my issue was that my label text type was marked as “Plain” and hence some fonts were not showing in the dropdown in the Storyboard. As soon as I changed the text type to “Attributed”, all the fonts appeared in the dropdown.
Hope this’ll help someone stuck with the same issue.