The only site you should download Flash from is the Adobe site otherwise you may subject your Mac to malware.
Flash is not available from the App Store anyway.. it's written by Adobe. It's not an app, it's a plugin. Big difference.
If you are having problems with Flash streamed content, do the following:
Assuming you are using Safari for video, quit Safari.
Open System Preferences > Flash Player then select the Storage tab. Click: Delete All
Now uninstall the Flash plugin then reinstall new > Troubleshoot Flash Player | Mac OS
Very important to uninstall the currently installed Flash plugin first even if it's the most recent version.
Launch Safari From your Safari menu bar click Safari > Empty Cache
Now try a video.
BTW... if you have the ClickToFlash extension installed, that can prevent Flash based video from streaming. It can also be installed as a plugin in /Library/Internet-Plug-Ins.
And check to see if Safari is running in 32 bit mode. Right or control click the Safari icon in your Applications folder then click Get Info. If the box next to: Open in 32 bit mode is selected, deselect, quit then relaunch Safari.
edited by: cs