Scampin!!!!!!

HELP!!!!! I bought a brand new master cylinder, installed the brakes and bled them. After bleeding them I go to hit the brake and it goes right to the floor. Ive got no pedal. But if I pump them 2-3 times i have a good hard pedal. Then I lose it again. Brakes were bled numerous times and there seems to be no air in the lines. No leaks so I dont know what else to do? Any gurus out there that maybe had the same problem?