SKS functionality suddenly lost

I've read PriusChat threads on this subject and i think i know what i have to do but want to check with live humans if possible.

My car is 2007 Prius, Package 6, Navigaton, i got it in January 2009 with about 28K on it. It now has about 82K. I never replaced the battery in the SKS FOB before, it always worked, it's probably original to the car, 2007.

About 3-4 days ago, i couldn't start the car, there were signs it wasn't the car battery. i called Auto Club and he said my FOB battery was dead. Need to replace. He put the FOB in the port to show i could start it that way, so i could use it. I'm used to having all the smart functions ever since i got the car so it's big difference, using the mechanical key to lock the car, etc.

I have a spare FOB and when i tried using it, its battery was working but it didn't have the smart functions, no SKS. It seems to only be able to open the drivers side door remotely, lock and unlock. No other doors, has to be in the port to start the car. I put a new battery in the one with the dead battery and it also is working now but not with SKS. Same functions as spare.

Is there a likely reason why the FOBs would stop having SKS? Does it have something to do with the old battery dying on one of the two FOBs? I read that what gets un-programmed is in the car, not in the FOB, so that would make sense that both FOBs don't function (SKS)?

i would like to ask if there's any way of knowing what happened to the car to cause it to unprogram itself from the FOBs.

I want to confirm that what i have to do now to get SKS is go to a dealer to get a new FOB, or two new FOBs? i do have to get at least one new FOB, is that right? Nothing can be done to get the existing FOBS to go back to having SKS again, that is now over?

I had to have Toyota do this once before but i don't remember why. I have the invoice, it's from March 2018.

When i had the work done for the key FOB, the invoice says that the customer concern is: Please program and add one Master key FOB. The correction says: Added and programmed one key. It says the part is: Transmitter, electronic. Part No 89994-4706. The total charge for parts and labor is $357.

i guess i'm mainly asking what is the easiest/fastest/least expensive way to fix the problem i have which is to get SKS function restored.

i'm in the San Fernando Valley, Los Angeles north. Does anyone know of a Prius competent mechanic recommended for this service in this area, north Los Angeles. Thanks for any info.