Gravity brake bleed not working

Shadow said

Have new master, all new slaves, empty brake lines, everything is dry except for the master which I bench bled and is full of dot 5. Have slave bleed valves open down below.
No fluid will come out of the master.
Do I need to push my brake pedal down and put a wedge in to keep it down? Even when I was mounting the master after bench bleed no fluid was coming out of it before even attaching brake lines.

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If you did a bench bleed and had fluid from front and rear reservoir out of the master then your problem doesn't sound like the master.

I had the same problem once,
It turned out someone pressed the brake pedal to the floor before the old master was removed.
New master bench bled and installed when trying to bleed I got nothing out of the right rear..or any other bleeder.
Everything was clean.
my co-worker (licensed mechanic) said the prop valve was moved with air in the system causing a blockage by the prop valve itself.
I loosened the lines at the prop valve and tapped gently on the brake pedal (NOT PUSHING ALL THE WAY TO THE FLOOR) and started getting fluid.
Something to check even though Its not very common.