The thread you posted to was about a new implementation of "Retrieve Metadata for PDF" in the Zotero beta, which I assume you're not using. If you're trying to retrieve metadata for a large number of PDF files, you can certainly try using the beta (since "Retrieve Metadata for PDF" in the current version will stop working if you try to recognize too many files at once due to throttling by Google Scholar), but it's not clear to me exactly what the problem is that you're facing.
Also note that using Retrieve Metadata for PDF isn't the primary way to get data into Zotero, though the changes in beta will make it somewhat more feasible as an option (and we know that people new to Zotero often want to add large numbers of PDFs at once).
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Also note that using Retrieve Metadata for PDF isn't the primary way to get data into Zotero, though the changes in beta will make it somewhat more feasible as an option (and we know that people new to Zotero often want to add large numbers of PDFs at once).