Reactivating/reprogramming a key fob on the same car??

Is it possible to reactivate or reprogram a key fob that had once been working on the very same car? Today I have 1 working fob and two fobs that once had worked but stopped. Years ago, dead fob 1 wouldn’t flex on the unlock button. Got a new fob that my mechanic programmed—this new one is my one working fob today. (And tossed the dead one in a drawer) Dead fob 2 had been working but the case was getting worn and the red panic button fell off. I got the bright idea to swap the case with one I bought on Amazon. But I took it all apart and then got frustrated putting it together and tossed it in a baggy in a drawer ( I know! My bad!) Anyway, a mechanically inclined friend came over today. He put in new batteries and reassembled the fobs. They are alive but cannot unlock the car. Inside the car, the dash shows the red key blinking but when my friend tried to start the car, the key flashed yellow. We were thinking we could try the chicken dance but I read somewhere that it only works for brand new keys. I don’t understand how these fob could get unprogrammed. Does having a dead battery in the fob cause the programming info to get erased? (Or with fob 2, having it completely disassembled and sitting in the drawer for months?) Also I need to get two of the mechanical keys cut. I have the “blanks” that fit the fobs. Where do I go —a locksmith? For house keys, the hardware store can be hit or miss, but they have a stash of keys so they can easily retry again. Thanks in advance for your help! BTW I’m getting ready to sell my beloved 2006 Prius (just bought a 2025 Prius Prime). I’ve been a lurker on this forum for years. Thanks for all your help and wisdom. ❤️

 

No.

When I put it in the slot the red key still flashes but when I push power, no yellow key flashes. If I repeat with dead fob not in slot, pushing power causes yellow key (with !) to flash.

Somehow I never played with this before. With only the good key in the car and in hand, that red key flashes. (Don’t remember this—guess I’m not observant). Good key in slot, red flashing key stops. With good key, car starts with and without putting it in the slot.

Any hope for the dead fobs? The red dot on them is flashing and we put in brand new batteries.

 

Good news—I found my second working key, with the missing red panic button. (I had been surprised I’d let myself have only one working key —yikes!) So my plan is to hand over these dead fobs to the next owner. But the question remains if they can be reprogrammed. If anyone has thoughts, LMK. Thanks!