My brakes weren't working so I had brake specialists take a look. They say no physical damage and told me it needed flushing or maybe a new master cylinder. They flushed the system and told me the master cylinder was out, the FR and RL brake weren't working. I replaced the MC and bled all the brakes and now they still won't work at all now. Before I swapped out the MC the car would stop slowly with the other two brakes still working. Does anyone have any idea what could be wrong? Thank you, I'm new here and still trying to move around on here.