By chance did you evacuate the reservoir and refill before bleeding? Often this drains the rear half of the reservoir and there's a trick to getting it filled. Meanwhile your heavy pumping on the pedal sends air throughout the system making it that much more difficult to bleed. Hence the benefit of a power bleeder.

If time is not an issue, fill the reservoir to the brim and leave the problematic bleed valve open. See if you can get gravity to bleed that line for you.

None of this will help a bad master cylinder.

Sixto
87 300D