flashplayer

I am using windows 8 on my pc.  All diagnostics I've tried tell me that flash player is installed and ready to run.  However, when I try to run a program that uses flash  player, I get a message saying I need to install this.  It most regularly happens in a chat room on the site www.atraf.co.il  I have resorted to entering this site from firefox but this is no longer possible since firefox is suffering from  an overwhelming barrage of unwanted advertising.  How can I fiss this problem?