Clogged brake lines?

I've seen flex hoses do that. I've also seen lines get pinched from floor Jack's. But are you sure you have pressure coming out of the master? I only ask because it is possible for a piston to "overextend" inside and block the passages. I had one do that to me and ended up cracking all 4 bleeders loose and stabbing the pedal one time real hard then closed off the bleeders, It worked! Something inside jostled back into place and all was good after that.