2012 Prius 4 not starting

I don’t see ready illuminated, is your foot on the brake pedal?

Does the dome light come on?

Any recent maintenance or damage?

 

I’d definitely start by replacing the 12V battery. It’s due for replacement at that age and it can definitely cause what you’re seeing. It’s a special battery, installed in the rear right side of the car (hatch area). You could try charging it, but I’d just buy a new one and most likely you’ll be on your way.

 

Check the voltage on the 12 volt first, with a digital multimeter. At the under-the-hood jump point in fuse box. Do this first thing in the morning, pop the hood the night before: that way you'll access the engine bay without "waking up" the car in any way.

Rolls Royce would be to hook up something like a Solar BA5, directly to the battery posts. Besides reading the voltage, this will do an electronic load test of the Cold Cranking Amps, and give you a verdict.