Did you loosen the butterfly nut as much as possible and move the little flap/latch ?
Yes, the problem was lifting it up on the lower lip
I've never messed with this grill, just seen pictures of it. I'm presuming that when you slide the tank into the bottom of the grill, it's dropping down into the hole and you are having trouble lifting it up high enough to get it on the hanger.
If that's the case, put a piece of wood (like a 2 x 4) across the hole. Maneuver your tank into the bottom of the cabinet and onto the 2x4. aaaaaaaaaaaaaaaaaaaalet it rest there while trying to seat the collar of the tank on the hanger.