I have this issue as well, specifically with this article:
https://nuclearmonster.com/2017/03/the-new-ipad-cheap/
The json file that the plugin generated is in fact empty, zero bytes.
I’ve enabled the debug option to generate an email, no e-mail was sent.
In this case, I have been having problems with my host (DreamHost) throttling the memory usage of the site and they have been not very helpful in debugging it, so occasionally the php processes are killed as they try to upsell me to a VPS without giving me the tools to debug the issue.
I suspect this happened to the apple news plugin when it was trying to generate the json for the article, and that’s why it is empty. Not at all sure, but that’s the most obvious reason.
In that case, I am not sure if updating the post should regenerate the json from scratch, or not. I haven’t had time to look at the code for the plugin to debug it further.