Click the Download button to download the OS X El Capitan installer. Note: It’s always a good idea to run any other updates that might be available before running the OS X update. For example, this morning my iMac had an Xcode update and a security update waiting, so I ran those with the knowledge I’d be updating to OS X El Capitan later.
I have had this problem also, but after going into the Applications folder and initiating the install, it goes thru some gyrations, then restarts, but El Capitan is still not installed. Note: My MacBook Pro has Parallels installed to enable Windows programs, but it was not open during the install. If you are trying to install Dell SonicWALL NetExtender (it's a VPN client) on OSX El Capitan, you might run into a situation where it won't connect to the VPN. Here’s how to upgrade from El Capitan to Sierra. Download High Sierra from the App Store. High Sierra is available for download from the App Store. To get it, follow these steps: Open the Mac App Store by simply clicking on the App Store icon in the dock. Navigate to the Featured tab. Find macOS Sierra in the rightmost column and click on it. Finally, if the above solutions do not work out for you, what you can do is download and install the operating system in macOS Safe Mode. This is only for the users that are trying to upgrade from their current version to El Capitan. This means, if you do not have macOS installed already, this will not work for you.