Adobe Flash Player dosn't work on some websites

Hi there, I use Firefox 46.0.1 and has installed the latest version (21.0.0.242) of the Adobe Flash player. I can't load some flash content in some websites (e.g. BBC, tudou...).  I got the error message "The Adobe Flash plugin has crashed. Reload the page to try again."  But after I reloaded the page, nothing improved.  I even deleted all flash player browsing date, removed flash player cache and disabled flash player hardware acceleration, it still doesn't work.   Please help, thx.