After much frustration and trying many “solutions,” I finally solved MY problem with the Flash Player in IE 11.
Try this: In the video application, e.g. Facebook,
1. Right click the video image
2. Select All Accelerators
3. Select Manage Accelerators
4. Select Toolbars and Extensions
5. Enable Shockwave Flash Object
6. Close and restart the application.
Video should now play.