Trailer brakes won't "firm up" after servicing

I just installed a new swing tongue on my Boatmate trailer. The process included taking the UFP A-60 brake actuator from the old tongue and putting it in the new tongue.

The whole process went pretty smooth but now I can't seem to get the brakes to build proper pressure. I have a helper that's using a 2x4 as a lever to compress the tongue during the bleeding process and that's working fine. When I crack the bleeders there is a steady stream brake fluid with no apparent air bubbles.

We've ran about 1.5 pints of fluid through the master cylinder and still when we go to compress the tongue it travels all the way to the end of the stroke.

The trailer has disc brakes and they are on one axle only.

QUESTIONS:
1) The trailer has the reverse lockout solenoid. If that solenoid was somehow stuck in the energized (open) position, I wonder if I'd have these same symptoms???

2) Could I have screwed something up during the installation?

3) Would you expect that I'd need to run more that 1.5 pints through the system considering the M/C was uninstalled and reinstalled?