Do you have a wireless connection? El Capitan Has problems with wireless connections. It even drops them for no good reason. I had to Go wired on mine. So plug an ethernet wire in and see if its just your WIreless connections. If your using wired connections then never mind.
Thanks for the suggestion. I was able to restart and complete the installation with the wireless connection, and when that happened, I got additional errors with the request to retry. After a few tries, Technical support accessed my computer remotely, did some cleanup and was able to install it after about 30 minutes.