I was trying to use a graphic tool on a photo printing website which told me that I needed to update Flash Player. I followed the advice on the Adobe website and enabled Shockwave and Activex filter. Still didn't work. I checked on the Flash website and it told me that Flash was not installed on my computer (which I find hard to believe). Anyway, tried to update using the link on the Adobe website, which enabled me to download the update file, but when I click on it an error message appears "security update for windows (KB3099406) is already installed on this computer". Also in Flash settings the option "Notify me to install updates" is ticked, although I don't remember being asked to update ever. The whole page is greyed out so I cannot change it to either automatic or no updates.
Not sure what to try next...any help welcome !
PS I have had issues with videos not playing on this computer and just showing a green screen, not sure if this is related
Looks like you have a Windows 8 or newer system. If so, Microsoft embeds Flash Player in IE and all updates are distributed by Microsoft via Windows Update. KB3099406 was the Microsoft Update for last month's release of Flash Player. If you already have that installed it's why the error is being returned when you try to install it again.
A new version of Flash Player was released yesterday. Please run Windows Update to download the update (KB3103688) or download it from the link at the bottom of the https://support.microsoft.com/en-us/kb/3103688 page.
Another thing to check is to ensure the graphics drivers are up-to-date in your system. If not, I'd recommend updating the graphics drivers.