Clogged brake lines?

Overview of the system. 4 wheel drum brakes, manual, with a new (rebuilt) master cylinder and new front lines. Rear lines look good, as does the rear feed line.

The boy and I went to bleed the brakes last night. Bench bled the master cylinder, then we started with the rear because that's how I was taught (furthest to closest), passenger side. I tried vacuum bleeding, but as much as I tried, I couldnt get anything out of the bleeder. Switched to driver rear, same story. Had the boy jump in and pedal it... nothing. Fluid level in the reservoir is not going down. Fronts bled out perfectly.

As a diagnostic move, I opened up the passenger side rear bleeder and put the vacuum pump on the driver side rear. The lines on the differential (after the split) cleared out with a problem. So I think I have the problem isolated to the feed lines between the prop valve and the junction. Problem is, I have never heard of a CLOGGED brake line before. Certainly not to the extent where NOTHING gets through. FYI the parking brake is not hooked up if it matters... dont think it should.

Anyone else experience this?