Sounds like the energy absorber(bumper shock) is stuck in. Take a block of wood and a sledge hammer and place the wood against the edge of the bumper and give it a few blows with the sledge. Go easy, you're just trying to pop it back out not beat the hell out it. Be careful the wood and/or the hammer doesn't hit the body.
A better way would be with a short ram on a porter power from the chassis to the bumper, or a big bam-bam with the big hook attachment.
Just remember those shocks are under very high pressure and can burst if pushed to far out, and don't try heating them!