try to reinstall os x el capitan...
Step 1: Boot into recovery mode (CMD + R while boot up)
Step 2: Click on reinstall OS X (Make sure when you are in the installer it says, Reinstall OS X El capital, if not DONT DO IT!, you will be downgraded to os x Yosemite
Step 3: Click continue and at end
Step 4: Reinstall it by click on restart after the mac has downloaded all the components!
Isn't that second one the shortcut for Internet Recovery? Although I think Internet Recovery only downloads an image for the OS that came with the Mac, rather than the latest, which I find weird considering Apple's current stance on OS updates.