Brake pads fixed, parking brake, car won’t start.

I had my brake pads replaced a few hours ago. The man pumped my brakes and made sure it was running. About 20 mins ago I tried to leave and the light ! P brake (which I assume is the parking brake) came on and the car won't start. I checked all fuses, engaged and disengaged the parking brake but it still won't start. What can this be and how do I fix it?
My car has an automatic transmission.

– Brake pads fixed, parking brake, car won’t start.