Remote not unlocking car after long hiatus

I haven't drove my 2005 Prius in about 1 month, maybe more. It's just been sitting in my driveway and I have been too lazy to sell it. I finally got around to putting the add up today, then I went to open it up today with the remote and nothing happens. No beep, nothing, so I have no way to get into the car. I can see some red flashing car light in the car, that is all, but it's always had some sort of light that flashes as kind of like standby when the vehicle is parked and shut off I believe.

I recently got a new hybrid battery from GreenTech that had a 18 month warranty. I'm only 6-9 months into the warranty and hopefully that is not what it is. Maybe it's just a faulty remote. But seems strange this has never happened before, and only after I let the vehicle sit for a month without driving.

What can I do to get into it? What should I look for? Could it be the regular battery instead? I do not want to get the vehicle towed or to spend too much money on it. It has 225k miles and I'm trying to unload it for $3,000. Already bought a new 2011 Prius that is my replacement.

Thank you for any help the community can provide