Flash Video Doesn't Display, Internet Explorer Does Not Run ActiveX Content
On Internet Explorer 9 or better, Flash video will not play, other sites that require Flash will not operate properly, and sites which require other types of ActiveX content do not operate properly.
Uninstalling Adobe Flash and reinstalling does not help.
This may occur if ActiveX Filtering is enabled in Internet Explorer. To turn it off, go to the Tools menu and untick ActiveX Filtering.
Note: using YouTube.com to test Flash video is not useful as it uses HTML5 on most browsers.