El Capitan usb upgrade is stuck at os x utility

I have a late 2008 MacBook Pro with Yosemite installed. I am not able to use the App Store updater so I have an El Capitan installer on a USB drive. When I boot into it, it eventually goes to the OS X Ulitilty with an option to upgrade or install. When I click on that, it doesn't do anything. What am I missing?