Failed to load URL when using ABCpdf on Azure

Question

I'm using ABCpdf to generate a PDF from HTML.

int id = theDoc.AddImageHtml(html);

It's working fine in my local environment but throws an error when running on an Azure server.

Exception:

Failed to load URL data:text/html;charset=UTF-8;base64,........

What does the error mean and how do I fix this?