Adobe says I've already installed Flash Player, but several sites say I need to install it to better view their content. Why?

When you ask a question you need to provide some basic information

-Forum quick start https://forums.adobe.com/docs/DOC-5601

Mac or Windows, and EXACTLY which version of the operating system?

Recent Mac AND Windows operating systems have been known to cause "odd" problems

Are you using a computer Administrator account with full read/write permission?

Exactly which version of the program do you have that is causing problems?

Do you have the latest Player?

Getting Flash Player https://get.adobe.com/flashplayer