One Fob stopped working, NO red light, Battery fine, Prius 2014-plugin

I am stumped. Maybe someone can help. The key fob that does not light up will work when held against the ignition switch. I also have a spare fob that works so it is not an emergency (yet).

1. 1 key fob stopped working periodically and the dashboard said remote battery low.
2. I changed the battery and it started working.
3. After a few days, it started the same problem: remote not working, car dashboard warning. Sometimes the problem would go away.
4. Holding key to the ignition switch works.
5. The remote's led does not come on when it stops working.

Battery check: > 3.1 V.
Continuity check passed => Voltage on the board: I checked if the voltage on the printed circuit board was approximately 3V and it was correct. I used a meter to test the voltage between the ground plane and the the positive and it was correct.

So it is not a loose connection in the fob. What do I do now? I can still use the keys in a pinch so I am not desperate.
Q 1.: Is there a reset for the FOB that will allow me to at least reuse the key. It is from Toyota.
Q: If the led light does not come on the fob, does it mean it is toast?

 

Additional Info:
1. The circuit board has: 271451-5290 (picture below)
2. The FCC ID seems to be: HYQ 14ACX. I could distinctly read the last 5 characters and the first three characters seem to be HYQ.

 

I think both ideas are good. Gave me the idea that maybe I should borrow an adjustable power supply and just straight out give it the 3.3V it demands. I got the batteries from Amazon so they could be just under par.

 

My coworker got his spectrum analyzer, a variable voltage supply, and a DMM. We supplied 3.01 V to the battery terminals, and the LED lit up. The spectrum analyzer showed the RF blip.

We then put the battery back in, and the voltage drops to 2.0 volts when we press the button.
Diagnosis: bad batteries from Amazon

I opened the other working fob and realized that removing the battery sitting snugly was not worth the trouble anymore. But thanks for getting my brain going in the direction I should have gone in.