Responsive project, using Advanced Actions. Suddenly a slide that was working weeks ago now refuses to load in Preview. I recreated it in a separate project and it runs fine, but when I copy it back into the original project it again refuses to load.
Which Adobe software are you using?
If it works in one project but doesn't work in another, you either have
1) critical code errors or
2) script incompatibilities.
That's all I can say without a lot more info.
You might want to post this question in the appropriate Product forum i.e. Dreamweaver, Muse, Business Catalyst, etc...