Could not render the url. Could not get image from url.Navigation timeout

I've got a ASP.NET web application which contains the Winnovative HTML to PDF Converter.

This has been running for over a year successfully generating PDFs

However, this is no longer working, and the error being returned is:

Could not render the url. Could not get image from url.Navigation timeout..

I've checked the Winnovative FAQ and they suggest adding a NavigationTimeout to the instance of the PdfConverter. I've added the following:

PdfConverter.NavigationTimeout = 500

However, this has not fixed the error. Furthermore, the page being converted only takes a fraction of a second to load when loading directly in the browser, so I don't believe its a performance issue with the page being rendered.

Has anyone experienced this problem before? Are there any known solutions/causes for this?