Key fob and keyless entry/central locking not working

[Newcomer]

Japanese import Prius 2018 key fob has lost all connection to the car's keyless entry/central locking system. This happened after locksmith made a spare key while the 12V Battery was low. We jump started it and the vehicle starts with the fob but the fob won't lock the car. 

Locksmith thought it was the 12V Battery initially. We changed it and he tried again a few days after and it still won't respond to the key fob. Now he is saying it may be that the receiver module may be aftermarket and we have to change it to the UK frequency. I am not sure what to think since it was working before. 

We did another spare key for the same make and model (we had two) and it worked on the other one - no issues. Only difference was the low Battery message that showed on the first one. I have checked fuses, swapped batteries, nothing works. 

Has anyone seen this before and how can it be fixed? 

[flash22]

Turn the keyless entry and start back on (a low Battery or disconnected Battery defaults the keyless lock to off it does the same with a flat fob battery)

Not 100% on the prius it will be in a menu on the touch screen under general - vehicle - customizations

[Newcomer]

It does not respond even after doing this. I managed to test Key diagnostics in tech stream and the vehicle recognises when I press the key fob meaning key fob still communicates with the vehicle but it just won't respond.