Issue also described in: “pandoc-reference-list-preview-doesnt-work-on-one-specific-reference-in-one-vault/81916”.
But that post has closed, and the solution there did not work for me.
I had found that the issue was on Zotero’s side with the BetterBibLatex plugin being out of date. I had noticed this when I saw that new added items in Zotero did not get updated with citekeys.
Solution is to update/reinstall the BetterBibLatex plugin.
Thanks.