78 Corvette brake conundrum...

Helping a customer with his 1978 Corvette. We put four new brake hoses four new brake calipers 2 front rotors and bearings. Brand new master cylinder bench bleed. Vacuum bleed all the brakes starting with passenger rear ending with drivers front. Then to make double sure did a short gravity bleed on all four just to make sure. NO BRAKES...???...:BangHead:...

Who did the master come from?
I had a couple parts store units a few years ago that wouldn't push fluid. Brand new, right off the shelf, something was up with the piston bypassing fluid. Sucked!