Is it your pump? dunno. why don't you pressure test it.
what lift cyl type?
plumb hyd gauge capable of 3000 psi into the work port on the valve or couple to the hose in place of the lift cyl.. see what she makes deadheaded.
if it makes good psi deadheaded ( 2000+ )
and still no lift, then test lift cyl if DA. if you have 2 test each seperately. 1 blown parallel cyl will teke out both..
if it is a da lift cyl, remove the hose to the drop port and pressurize the lift port. if oil just blows clean thru.. packing is gone