Three beeps when I close the door and car won't lock

When you open the door, does the car beep until the door is closed?

It sounds like your car is in accessory mode, which can happen when you shut the car off, but have a load on the 12v outlet. It's sort of a "bug" in the Prius, but it has been well documented and confirmed my several posters in another thread. All of your symptoms fit that.

Do you have anything plugged in to either of the 12v outlets? Either the outlet by the seat warmer buttons under the "flying bridge" where the shifter is or the outlet in the compartment between the seats?

 

That's exactly what mine does if the car is on.

 

You may have left the car on “ready” and did hit the start/stop button to turn car off. The door locks didn’t engaged because car is still ready, the 3 beeps confirms that.

 

"I must be missing something."

Hitting Park and then pushing the power button will not turn the car off.
You must put your foot on the brake, THEN hit the power button to turn the car off.

 

Since my car is right outside, I went to test. At least on my car, there's no requirement for putting foot on brake.

As I indicated in my earlier reply, you can turn the car off and the car will appear like it is off but is actually be in ACC mode, which has every symptom you described. Do you have anything plugged into either of the 12v outlets?

There was a whole thread on this about a year ago. When there's a load on the 12v outlet the car will enter ACC mode when turned off, rather than turning off, despite appearing to be off. The three beeps and remote fobs not working are telltale signs of this.

Also, when you open the door, does the car beep until the door is closed?

 

I just checked mine, too, and no requirement for foot on the brake, but I've noticed scenarios where I DID need to put my foot on the brake, then push the power button to shut down the car. My mistake...

 

I have never needed the brake pedal in order to shut off any of the three Gen 2s, the PiP, the Gen 4, or the Prime. Just the power button.

So, if the car isn't still in READY or ON or ACC, my next check would be if the spare fob is in the car. My wife does that to me ALL ... THE ... TIME!

 

She’s due for a trade in.

 

it happens all the time for the people here. Some feller did the same thing, except he didn’t put in park. He went to move some debris on the road and went back to where he park and the car was down the road.

 

You may have another key inside your car. It won't lock if there is a key inside.

 

Just did a test with my car since its right outside. It locks just fine with a key in the car, using another key fob outside the car. It won't lock if the car is in ON or ACC mode.

OTOH, what you say is true if you lock the car with the electric locks and then shut the door with the key inside. The locks will automatically unlock when the door closes.

And the difference between those two scenarios it make sense -- Toyota is trying to keep you from locking yourself out of the car. If you are using the key fob outside to lock the car, it doesn't matter that there's a key inside because you have a key outside and can get back in. But if you are using the electric locks, then you very well may be locking your only key inside, so the car won't allow it.

I still say that the clues to the OP's issue to this are the constant beeping with the door open and exactly three beeps when the door closes. But the OP hasn't said whether there is anything plugged into the 12v outlets.

 

As I said several times above, your symptoms are 100% consistent with being in ACC mode. When you pressed the stop button you were in ACC mode, not OFF, and that caused the three beeps and fob not to work.

But I have asked you several times for specific additional information to try to help you which you have not provided, despite posting several times.
As they say on "Shark Tank," I'm out.

 

If the car is in READY and you push the power button once, that turns it off.

If the car is off, if you press the power button once with your foot on the brake, that turns it back on. If you press the power button once with your foot off the brake, that puts it in ACC mode. Press it again with no brake and it goes to On mode. One more brakeless press turns it back off.

This is clearly described in the owners manual and there is no way to customize this pattern.

So, if you hit the power button twice without the brake pedal, if was in accessory mode when you pressed it the first time, which put it in ignition on mode. The car won't like being locked from outside when in accessory mode. The second press turned it off.