'09 parked for 1 year, keyfob won't work. 12V battery issue?

I have a 2009 Prius that has been parked at a family member's driveway for about 1 year and 2 months, much of it in cold winter weather. They were able to turn it on and re-park it for a few months, but eventually it stopped responding to the keyfob unlock (keyfob battery is brand new). No one can enter the car because my mechanical key has never worked (I suspect the keyfob + mechanical key is not Toyota original, as there is no logo on it, it's just all black. I suspect it's simply a replacement from Amazon).

I had the car inspected by Toyota in 2020 and they told me the 12V battery would need to be replaced at some point.

I'll be heading over there in one week to try to get it up and running.

Would you all be able to tell what you suspect might be the issue? I assume my first order will be to get a tow truck to get the door open, then we'll attempt to boost the car and see if it starts.

Thank you!

 

Hey there! The mechanical key sadly has never worked since buying it from previous owner. I suspect the keyfob + mechanical key were bought off Amazon.

Amazingly, also, I have never been also to open from inside using mechanical latch. Good times.