Flash player is being replaced by HTML5
Basically its the software giants making browsers catch up to a technology that exists without a 3rd party program (Flash)
You may experience it working on some sites and not others so try a frew sites as it may be installed but not working for those sites.
* If your installing you may have to go via the addins route in your browser? Check your browser for more details.
To help you solve the problem.
1) Reboot your computer. (Then its a fresh start).
2) visit http://get.adobe.com/flashplayer/
(untick the extras).
3) that page should tell you if its installed correctly.
If its installed correctly then you may have to uninstall it to re-install it as it may be corrupt.
One step at a time. Do the above and let us know how you get on.