Meteor and above not rendering with PDFLayer API

When running Meteor, the third-party PDF tool PDFLayer was working fine. After upgrading to Meteor 1.5 the api returns a blank PDF.

Upon further testing, I have a couple of sites running Meteor, which work fine with PDFLayer and a couple of sites running which return as a blank PDF, so I assume something has changed at some point between these two versions but I’m not sure what…any help is much appreciated!

I’m making the api call with document_url to PDFLayer, not document_html