you have a blockage, and sods law will say its on the master cyclinder or one of the pipes coming from it, but tbh i would start with the brake hose, take the caliper off and bleed the brake to see if fluid comes out, if it does and comes out fine the problem is with the caliper, if it dont, remove the rubber pipe and do the same, if it dont flow out of the metal line, you will then have to trace it back (to make sure you get right one) and dis connect it from the master cyclinder and again, pump the brake, if you still get no joy i would advise a new or good known working s/h master cycliner.

if or course you do get fluid them you must clean the pipe thats blocked out, a bit of electrical wire stripp (single core lighting wire for example) is just the job.

if you have abs, do as above but do it befor and after the pump