2014 Prius Smart Key Proximity Access stopped working

Hello prius owners,

I just got my first used prius v and may be missing something. The proximity access worked for a week and then stopped. I have tried the sks button under the dash and the smart key option on in the setup.
The battery is at 3v and the unlock, lock and engine on/off works fine.
I have also tried the other fob.

Any ideas?

 

Anybody know how Smart Key Proximity Access works or what to check?
Any links or diagrams?

 

Thanks Bisco,
Will replace and report- it now makes sense to me except I thought the batt were rated at 3v.


Later,
The new battery is 3.1 and no effect on problem. The 12v reads 12.2v standing and charge 14.6v.

 

No work or accident. I bought the car with 33000 mile from first owner after dealership prepurchace check two weeks ago.
The 12v goes to 11.7 after two minutes of lights on and then starts and runs fine.

New information: when locked the red light on fob does not start flashing as I walk closer.

 

Found the Problem!

I tried techstream and found that the car has three smart key not just my two. I looked under and over everything and found a third smart key stuck under the driver seat. Solved!! I can know go on with my life.

Thanks for helping me think this out.