What do my back brakes not work?

Thanks Pushrod. Brake pedal almost goes to floor and back brakes are not engaging. Bleeder screws are clear. Initially, I was getting a little fluid at the right rear bleeder. 4th time at bleeding....I got a lot of fluid with some air bubbles - then nothing. No air, no fluid. Tried left rear - nothing. The LSPV valve bleeds fine. I did notice if I moved the LPSV actuator arm with the bleeder screw open, maybe one drop of fluid would run out of the bleeder screw. Issue definitely seems related to this LSPV

it appears to be all the way up. Suspension loaded, axle supported by jack stands. I am not familiar with how the LPSV functions exactly (although I do understand it's purpose) - it appears to maybe be broken. The actuator arm that rides on the spring doesn't appear to do anything. Pull the spring down - it just kind of hangs there. Push the actuator arm up...is no resistance at all. Hits metal and stops. I suspect it maybe broken