2009 not starting or unlocking, but lights/beeps work

Hello, I have a 2009 Prius, 64k miles, and I just had a problem out of the blue.

It's been driving as normal since I got it 3k miles ago, even driving normally several times today, but after work I drove to the grocery store and then parked and shut off. When I tried to open the trunk, it wouldn't pop open as usual, wouldn't even make the noise. I tried several times on the handle but it didn't work, then I tried the key fob and that didn't work either. Whenever I pushed the lock or unlock buttons on the fob, the car would beep and the lights would flash, but the locks wouldn't engage/disengage. The power locks also wouldn't work when I pushed the buttons in the doors.

I tried this several times on the doors, then thought I maybe needed to turn the car on and off. When I pushed the power button, the light turned green but nothing else came on. No lights, no ready button, the panel didn't light up, no A/C, nothing. When I pushed the power button again, the light in the button turned orange and the orange "check engine" light came on, followed by the standard clicking sounds it usually makes on shutdown. Pushing the power button a third time turned off the lights.

I have no idea what's going on. I don't think it's the battery (as said, lights work fine and the headlights, too), and display lights like the "lock" indicator work. The key fob flashes its red LED when pushed and it can elicit a "beep" from the car, but the car won't lock or unlock unless I use the physical key. I don't think the battery in the key fob is dead either. What's going on?

UPDATE: It was the starter battery. Thanks everyone for your input!

The next day we tried to jump it, no dice. I had to get it towed and looked at, repair shop said the starter battery was completely blown, no amount of jumping would have helped. Wasn't too keen on buying a new one but hey, glad it wasn't a more serious problem.

 

UPDATE: It was the starter battery.

The next day we tried to jump it, no dice. I had to get it towed and looked at, repair shop said the starter battery was completely blown, no amount of jumping would have helped. Wasn't too keen on buying a new one but hey, glad it wasn't a more serious problem.