As mentioned in an earlier post "Split diagonal brake system". Left front and right rear are on the same hydraulic circuit. Right front and left rear are on a separate hydraulic circuit. If there is a difference in hydraulic pressure from one circuit to the other, (ie blown line or in your case, excessive air) The centering valve automatically shuts off the failed circuit, (it's a safety thing
).
You can manually center the valve and bleed both circuits, they make a special tool for it. Or, you can open one of the bleeders that is bleeding correctly, and give a quick jab and release on the brake pedal. If you do it with the ignition in the RUN position, you'll see the red "brake" light on the dash flicker. The trick is to keep the light off, then bleed as mentioned earlier, very gently.
If the light flickers and the opposite hydraulic circuit dribbles, the valve went overcenter. Open a bleeder on the opposite circuit and jab again. The dash light must be off when the ignition is in the RUN position to bleed all 4 wheels.