Any thoughts as to what? I agree but have run out of options to try.
IE 11, Windows 7
I specifically made a local folder and opened up the permissions wide open. The viewer opens up a document in the web directory as a default when the page loads just fine. Its just when you try to set the source to a local file. This has worked for years right up until IE 11 and Adobe DC>
I suspect it's more IE11 and not DC at all. You can verify this by trying to do the same kind of thing with an image file. If you see the same behavior, you know it's not PDF related.
You may try the .LoadFile("d:\test2.pdf") method.