vanguard

i just put on a new s13 booster and a s13 brake cylinder, i bench bled the cylinder with lines and put it on carefully back into the car, started bleeding and nothing would come out the rear driver caliper, so i moved to the passenger rear, and still nothing, im aware that a single line from the cylinder splits into two for the rear brakes... and the cylinder isn't pumping fluid or air or anything through the rear line, this happened to 3 clyinders it only pumps to the front right and left calipers..... what am i doing wrong???

P.S. Im looking for responses from REAL TECHS,... ive trouble shot everything... if questions i have all the details but basically the clyinder pumps out to the front right and left lines only and the line for the rears nothing...