No pressure in brakes, will not build up pressure to work?

The vehicle listed above is front wheel drive. We have already replaced the calipers, master cylinder and power booster along with new pads. The lines have no leaks and they have been bled several times. The drums and shoes are good. Now with all that being said the brakes won’t build up pressure to work. Please help me figure this out. It’s my daughter's car who is currently 9 months pregnant and due any day now. This is her car that we need to work before she has her baby. We are all at a loss of what else could be going wrong. It only build pressure up when turned off but as soon as you start it up it loses all the pressure, and the pedal goes straight to the floor.
We just need to know what else to do about it.