Bleeding brakes, no fluid to the rears

[19GMC63]

Ok, so yesterday I replaced a rear brake line since the PO snipped the old rusty one off because it had a hole in it. When I took the old one off, I got a dribble of fluid.
Well, I filled the rear reservoir, and began to bleed the rear brakes, and got nothing, no air or fluid. I tried pressure bleeding and the traditional two man bleeding and the bleeders are clean. I tried holding the metering pin in on the prop. valve with no luck, still no fluid to the rear.
Oh, and the front brakes (discs) work fine.

I'm stumped.

thanks in advance for the help/