Switched back to using the spineboy-skeleton.json the file. The new version I exported resulted in a failure to build skeleton data in SkeletonAsset. The exact line of failure in spine-c was:

SkeletonJson.c
Line 357
AttachmentLoader_newAttachment is yielding a null attachment.

Something about the new format is not working with the spine-c runtime. I re-added the old skeleton file and it's running again.