2009 Lincoln MKS won't start

What is your question?

I changed the battery in the car and in the keys. You dont hear no crank when i press the brake and push button. Asscessories come on but engine wont start. Also when the car doesn't start brakes will get hard and you can't push down on them. In a month the car did this to me about 8 times. I had brought it to 2 dealerships and my mechanic and they all tell me the car has to not start for them to see the problem. When the car didnt start twice i had got it towed once to my mechanic and once to the dealership. That morning i get a call talking about your started. We cant find the problem. I need help ASAP

What makes this problem better or worse?

I don't know

How long has your 2011 Lincoln MKS had this problem?

Month