No fluid when bleeding breaks?

2004 Ford windstar van break caliper and master cylinder replaced just trying to help my mother in law out i don't know if who previously worked on it did something wrong or what everything looks good but when I go to bleed there's no fluid on the drivers rear or passenger front the other two bleed as normal any suggestions on what it could be?

An airlock in the system.
Very dangerous.

Try bench bleeding the master cylinder. Go do a search on youtube for bench bleeding a master cylinder if you have no clue.

Brakes, not "breaks". You may have to bench bleed the master cylinder before bleeding the individual lines.

Check fluid flow from the front driver at the brake proportional valve.

Clogs at the bleeder are common. Remove the bleeder and take a look at it to see if it's plugged up. Use a paper clip or small drill bit or what not to clean it out. While it's removed you should see dripping at the caliper. If you don't have a drip then poke your paper clip in there and see if you clear a blockage. Continue to gravity bleed from there. No luck there then you need to follow the lines starting at the master cylinder and pressure bleed at the various connection to confirm fluid flow or not, someone can step on the pedal for you. With this effort you can isolate the problem area and inspect for a blockage.