I've got a web viewer whose contents are built on the following calculation:
data:text/html,"<!doctype><html> <body> <iframe src='[PathToWebHostedPdf]' style='width:100%;height:100%;'></iframe> </body> </html>"
On one computer it works fine, on another it does not.
Both computers are MacBook Pro late 2013, Running Mac OS X El Capitan 10.11.6, and both are looking at the exact same hosted web-hosted PDF.
The computer that renders PDFs just fine is running FMPA 12.
The computer that fails to render is FMPA 15. Instead of the PDF it's showing an all-black screen.
The same web viewer, renders the above iframe just fine when it points to a web page not containing a PDF.
And the computer is perfectly capable of rending the hosted PDF in Safari, Chrome, and Firefox, just not in the FMPA 15 web viewer.
So the problem seems limited to a version of FMPA running on this particular computer when viewing a PDF.
I found this: PDF file may not display in a Web Viewer or Interactive Container field | FileMaker and this: Unable to display PDF file directly in Web Viewer on Mac OS X | FileMaker, old posts which point the finger at Adobe Reader and the suggest to 'turn of enabled-plugins'. I don't have Reader, but do have latest version Adobe Acrobat DC from Adobe CC, and didn't immediately find a relevant option.