Typically when software applications are using an embedded browser window that wants Flash, they're looking for the ActiveX version used in Internet Explorer. If you've been installing Flash Player for Firefox, that's not going to help.
Fire up Internet Explorer, go to http://get.adobe.com/flashplayer and follow the prompts. This should resolve the issue for you.
If you're already using Internet Explorer on a Windows 8 or higher machine, then Flash Player is already a built-in component of IE. The problems you're running into may be specific to the intersection of those websites and Internet Explorer 11. (IE11 makes a bunch of changes to how the browser is identified, which may ultimately cause the sites to fail to detect Flash.) In that instance, the easiest workaround is probably to just use Google Chrome - http://www.google.com/chrome/ while we wait for the world to adjust to Internet Explorer's new approach.
Hello! I have the very same issue. The correct version of flash is installed on IE, BUT when opening the PC app, I get this same message. I too have
Installed the Flash app multiple times
Uninstalled the apps, Rebooted, and REinstalled the apps (pandora, pinterest)
I don't think it's the browser that is the issue here... but the App itself which should run without the browser open...yes?