Pdfcrowd API Error 452

I’m getting repeated 452 errors while testing out the functionality of the plugin;
I’ve added the shortcode inside the content as per documentation,
see “The [save_as_pdf_pdfcrowd] shortcode places a button in the web page. Clicking the button downloads the page as PDF.”

Ive switched between upload and development behaviours on the plugin setting page and I’ve gotten the same error on both. I’m testing this on localhost. Is there a plugin setting / shortcode parameter I’ve missed? As per documentation, I thought sadding the shortcode inside the page content would suffice.