2011 iMac 27' Not Network Restoring

My friend wanted me to restore their 2011 27' iMac, so I put all their images and crap onto a flash drive and started network restore (because for some reason that mac does not have a restore partition) and it showed the spinning world for a couple of minutes and went to the apple logo and did nothing else, it sat there for about an hour and nothing else. I am trying it a second time, I will stay in touch in the replies.

System Specs:

2560x1440 27' screen

AMD 2GB VRAM

Intel Core i7 2nd gen

1TB HDD

If it fails again I will post full specs but thats all I remember sooo....