All engine lights on, car won’t go into ready mode

I drive a 2012 Prius. I just did a head gasket change on it and it’s been driving fine for about a week except for one coolant leak where I didn’t connect a hose back up properly. (Since fixed.)
I drove it to work (1 hr commute) today with no issues, but after work it’s not starting. All the dash lights come on, but it won’t shift into gear, only neutral. I know two common causes with this are the 12v battery. I checked it, it’s reading 12.4v. Tried jumping it anyway. No luck. The other thing is the brake light switch. The brake lights are coming on fine.
One thing I want to note is that in certain cases, if it’s been a while since I tried to turn it on, the ready light will flash for a split second but then immediately go away. And I will hear 2 or three clicking sounds coming from the trunk.
So I’m at a loss for what might be the issue and I’m currently stranded at my workplace, the last place I ever want to be.