Hello all: I am currently trying to fix my boyfriends (2015 rMBP) computer as he had an error when booting that was a folder icon with the '?' in it. He doesn't have files stored on the device (mostly using cloud), so I figured I would take the USB installer and wipe the SSD and put a clean copy of OS X on it. Well now nothing is really working. I can get through the installer when booted up to the USB and then it restarts and apple logo installation bar runs its course. The it restarts again with my options to input my language, keyboard, and once I was able to get to the network selection process... However: this is what I keep running into, I get beach ball then all I have is the gray screen and the ball turns into a cursor. I have let it sit now for 25 minutes and it has done nothing. Other times it just does the apple logo, then gives me a O/ symbol like a NO! I have done PRAM reset and Verified and repaired the disk using first aid to no avail. Thank you for your help.