iPad 4th Gen
iOS 10.2.1
DropBox 36.2.2
GoodReader 4.12.0.
I have a simple HTML5 page with a video embedded in it.
http://www.astropix.com/test/test.html
It plays fine when viewed directly on the web in Safari, Firefox, and Chrome on the iPad.
But it won't play when downloaded in GoodReader...