I've been dealing with this problem for a couple days and I finally got it to work. First I downloaded decrypt9 and took the decrypt9wip.firm file and placed it in the luma/payloads folder in order to trigger the chainloader. That didn't fix it alone. So I went to system settings on my 3ds and selected the system update. after it completed, it did a mini reboot like always, and as soon as I saw the screen turn black, I held down the start button, and finally the chainloader popped up, I selected Godmode9 and it launched. I've done it successfully 3 times, so hopefully that means it wasn't a fluke, and it might work for other people as well. I don't know why it doesn't work for me when I turn my system off and then hold start while restarting. It seems to work only when my system does an automatic reset.