B2200 brake troubles

My son and I replaced the rotors and pads on his '91 truck and then tried to bleed the brakes. Apparently after filling the master/cylinder and starting the bleeding procedure, the m/c lost pressure. Now there is no pressure on the brake pedal. Initially the lines were bleeding at the wheel and then nothing. Tried bleeding the m/c but no luck. What would cause this? Cannot get fluid to purge from the m/c when removing the lines from the bottom of the m/c. Any hints?