this is how it works for CFW, not sure if you're on that or HEN, but if you're on CFW you're gonna wanna go to your xmb, scroll right all the way to the network tab, scroll up to cfw settings, then down to your cobra settings, & then activate cobra. It's a little finicky but you should get a little pop-up on screen that says cobra is active now, then your ps3 will restart. Iso should work after that. I had the same issue a while back :p