Lots of things COULD be wrong
Air in the lines..Bleed the crap outta that thing!
Air in the master
old pedal that is out of spec
Old fork, and pivot ball, possibly needs to be shimmed
Did you use all new parts, or used? I was having the same problem and I replaced everything hydraulic, and Im just barely at the right point. Next season I am replacing the pedal assembly, fork, pivot ball...and everything else I looked over when I assembled it.