I know that in the past if I've previously downloaded OS X El Capitan from the App Store I could download it again from the Purchased tab in the App Store, however now that macOS Sierra is out I'm not able to download it as it says INSTALLED (and grayed out) even on a system running OS X Mountain Lion 10.8.5. Pressing any key combination, e.g control, option, etc. doesn't change the button to DOWNLOAD. All other previous versions of OS X can still be downloaded from my Purchased tab in App Store as they still say DOWNLOAD and are not grayed out, thus active.

Mac App Store Os X El Capitan

Download OS X El Capitan. In your Mac/existing Hackintosh/virtual machine running Mac OS X, open the Mac App Store app and download the latest version of OS X El Capitan. This is a 8 GB download, so it's probably going to take a while. Once the Mac App Store app finishes downloading OS X El Capitan, an update window will pop up. So I finally decided to upgrade my mid-2012 MacBook Pro (running Mavericks currently) to El Capitan. Went to the App store (where a few days ago I successfully downloaded a Sims game app) and clicked 'Get'. Long pause, followed by the message: 'We could not complete your purchase.

Apple Store Mac Os X El Capitan

The image below is from a system running OS X Mountain Lion 10.8.5, does not have OS X El Capitan installed on it or even the Install OS X El Capitan.app on its filesystem, yet it says it's installed and grayed out.