TC55DA won't move

[Kraigs1]

Got stuck in deep mud so I locked the rear differential then put it in 4-wheel drive. When I stood on the differential lock I came off the seat so the engine stopped. Now I can't get it to move forward or backward. The drive won't engage. Made sure it was in gear. Tried low, medium and high. Tried gears 1-4 and forward and backward. Put it in neutral and pushed it with the bucket. Still won't move. Now I am losing power and can't push it with the bucket. Brake is off. Any ideas? Thanks.