Two leveling jack will not go down

I am only working on the forward one so far and it does not move at all, I jacked up the rig a few inches with my floor jack and used a big prybar and block of wood as a lever and nothing. I put a wood block under the jack and lowered the rig and it just sits on the block. Going to leave it like that for awhile. Any other things I can do? I assume cracking the lines at the jack will do nothing. I see what looks like a plug on the side. If I crack that will that help?

Thanks again for all the help!