A client has a music course that includes video files, apparently in .f4v format. When a customer buys the course, they download the entire set of materials to their hard drive. To run the course, they open an HTML file, which opens a window or tab on their browser. The lessons are all listed in that window. They are given the option, for each lesson, to read the lesson, do worksheets and quizzes, and play the video file (which is locally stored).
Over the past few years the course has worked flawlessly.
Just recently (starting a couple of days ago) clicking on the HTML file opens the browser, but all he gets is a blank, grey full-sized browser window. There's nothing to click, no words anywhere, and no error messages. It doesn't matter which browser is used (tried Safari, Firefox and Chrome, all on OS X 10.11, and Chrome on Windows).
The .f4v files are definitely present on the local drive. Double-clicking any one of those opens Adobe Media Player, and the videos will play that way. But they will not play through the browser, as they always have in the past. Also tried a couple of copies of the course just in case there was a corruption. A couple of his customers have reported the grey screen too.
I've gone into the browser preferences (Security) and made sure that Flash videos are set to play. As far as I can tell, it's set up properly. Other flash-based videos will play. On Adobe's site, their flash animations will play.
Has something changed regarding the playing of locally stored Flash files in a browser? Is there anything else going on? This seems to have just started this week. It suddenly won't play on my own Windows 7 laptop using Chrome either, and my flash plugin was not the latest as far as I can tell. Upgrading to the latest flash appears to have no effect on the problem.