I tried that actually (defaults write com.tumult.Hype4 AnimatedGIFEngine Apple)
So reverted.
But no luck, opened another project and that works ok.
So in the non working one , killed some fonts in the resources, to see if that was stopping it,.
No change, so added them back.
Then saved it as a template, then with the original note working one I was going to do some more deletions to see if any other resource was the issue but first tried to save it without a space the the export name. That worked,
Then re exported again but with the space in name again, and that worked..
Would you mind sending a quick report via the Help > Report an Issue… menu (and critically make sure the box to include logs is checked). Also please include the file you are working with.
After this can you try:
simply restarting your computer to see if that resolves it
(optional if not too inconvenient) use a different macOS user account or create one and try the export there
Save all open documents and then trash the Hype container (which will include prefs) via:
0. Quit Hype
In the Finder, choose the "Go > Go to Folder…" menu item
I sent over the file, via log report, but as I mentioned, it suddenly started working after a bit of tinkering (mentioned above).
It did not happen to all docs, although it did take me a while to try a different doc to find that out.
Not sure what really got it working, but it was not my restarts. Note when I say I changed the export name, that was only the export name not the file name.