2007 Prius Gen 2 - FOB stopped unlocking doors.

So this thing just happened, where on a few occasions I couldn't open the doors with the fob by pressing the button. I thought that the battery on the fob is probably dead.
I changed the battery, and after placing the battery I can see RED light on the fob blinking for about 20 seconds then it goes off.

Replacing battery on the fob did not help, as fob still doesn't open the door. I have to use manual key to open the doors, car drives and works like nothing happened.

What should I do ?

 

I just went to check the 12v battery to the service and turned out it was all covered in foam looking dead pretty much. We replaced it to a brand new one. I also got my middle dash replaced, which died sometime ago. All in all the fob started to work . It locked and unlocked the door. So obviously it was 12V battery right? ... WELL NOPE ....ZONK...I just came back tried to use the fob again and guess what. Can't lock / unlock doors again. Damn ...
Any ideas what could it be ? Immobilizer ? or something ? I 've noticed the red light on the remote keeps blinking when I am next to the door.

 

Something super weird is going on ...the lock/unlock is back again working, meanwhile the middle console screen that they replaced and was working, all of a sudden touch display stopped working.

 

I tried to wipe everything as much as I could. Would duplicating a key work ?