so...you can turn the steering wheel lock to lock VERY easily with wheels in the air? as in zero resistance?

then when you lower it, its unmovable?

see if you can VERY gradually lower it and figure out the exact point where the steering wheel becomes impossible to move..maybe something is binding and you will be able to catch it

some other things to think about:

maybe your pump is bad and not providing any high pressure? (no assist)

maybe your lines are clogged?

maybe you have the lines hooked up backwards to the box? (pretty sure thats impossible..)