What's it not doing  ?
They are not  at all complicated  , as already mentioned  it could be an easy tweak that may get it going again.  I bought  a good sized asian floor jack at least ten years ago , it has had issues that I was able to overcome  without difficulty.
On a similar topic ,  I have a very old hydraulic motorcycle lift bench , I think it was made overseas  , maybe not asia , possibly italy  . It's old and has been used commercially ,  About seven years ago I decided to restore it , repaint , rebuild the hydraulics , freshen it up , it leaked oil pretty bad . There are similar bike lifts still available , the units sold at pricess auto are an asian copy of the  lift I have .  I ordered a seal / overhaul kit to rebuild the hydraulics from one of my suppliers , after all it looked the same 

  .   I disassembled the entire lift , repainted all the pieces and started to rebuild the ram & foot pump mechanism only to find  that the main seal for the piston wasn't even close to what was needed !  My solution was to make a new piston , changing the design so that I could use the seal that was in the rebuild  kit , it worked well and is still in use with  no leaks .  
Try fixing it yourself  . 
I've seen new hydraulic units that were low on oil right out of the box.