Brake problem...not getting fluid to front passenger wheel.

[Tantrix]

It's getting close to road time for my '76 C10, so today I bled my brakes. All wheels bled fine with the exception of my front passenger side. Pedal was being pressed with 2 feet as hard as possible, and when I loosened the bleeder valve...not a single drop would come out.

Is this most likely the ribber line going to the caliper, or worse yet the metal line coming from the proportional valve?

Thanks.