Brake Master Cyclinder

[SebAu]

I have just changed my brake master cyclinder after a suspected rear piston failure (pedal was hard, removed rear line and no pressure). I have now installed a new master cyclinder, and bled the rear brakes. Thanks to some good advice I changed the rear rotors noticed that the caliper would not depress, I checked the rear line and found that even when the rear line was disconnected from the brake cyclinder the pedal will not depress ( front still connected). Is it possible that a have a second failed master cyclinder. Or is there another reason why the pedal will not depress and fluid will not bleed???