Key fob not unlocking/locking doors, red light flashes after battery replacement then disappears

Hi everyone,

Yesterday I discovered my 2004 Gen 2 Prius fob would not unlock/lock my doors and I am having some trouble figuring out the issue.

As soon as I replaced the battery in the fob the Prius blinkers simultaneous flashed and the small red LED light in the corner of the fob blinked for about 10-20 seconds, but after that there was not response from the fob. I can still insert the key into the car and it turns on and runs fine, but pressing the lock, unlock, or alarm button on the fob does not do anything to the car and the little red light on the fob does not flash. So it seems to me the fob is not dead because I got a reaction when I first inserted the battery, but I am confused about the lack of response afterwards.

I feel like I have ready every post on this website and others but almost everything is about smart keys and the small reset button under the steering wheel which I do not have. Any help is very much appreciated!

A little more info:
-I bought a new two pack of batteries, tried both of them and both resulted in what I described above
- My car does not have smart key functionality, so I don't have the little key button under the steering wheel to reset smart key function
-similar posts suggested that a button on the fob may be stuck, I get a good click and bounce back with each button press so I don't believe that is the issue