dodge guy wrote:
You need to pull that front piece down in front of the wood, then it should pull down into position. If it won't then there is something else damaged that's keeping it from happening. I would fix it properly and seal it all up real good. The last thing you want is a fast repair and have water leaked down the road.....literally!
This is the problem. You need to pull that piece on the left of the picture back out from behind that wood and it should pull the whole liner back down. It looks like it moved up and back from that piece of wood. My guess is it usually mounts to that piece of wood. Then you should be able to mount the upper round pieces back to each other with pop-rivets.