"Ready" mode problem

So my wife's Prius cut out on her in the middle of
the road. I noticed that I kept getting the
transmission lock is abnormal message, and the
light started dimming I was trying to find out what
the problem was that night, so I figured it was the
12v battery. I removed it, took the old battery to get
tested, and it turns out it had a dead cell. I went
and got a new battery today, installed it, and the
lights and screen and everything are working
perfectly now, but the car still won't go into ready
mode. I put the car into diagnostic mode, and it
says it's pulling 11.8v. Is that normal? What else
could the problem be? Could it be the brake
switch?