new battery.car fails to restart after shutting it off

First verify your battery connections are good. Juice has to get to the dash. How are you starting it? Jumping? Could be your Alternator is bad. Go to an Autozone and let them test your stuff. Starter could be an issue, does it click when you start, or nothing. Just a few things.

Old battery was putting out about 7 volts, enough for lights to come on but dim. New battery putting out 12V but have nothing. doesn't click when start. Everything is dead, i.e. lights, horn etc.....