It showed low battery for the key fob.
I changed the battery.

Now the car won't even unlock let alone crank.
mine is 2008 Infiniti G35 here in Qatar.
I changed the batteries twice and checked.
tried the rfid thing by placing the key near the push start button, no hope.
What should I do? Please advice 🥹

 

Are you sure those batteries are good? I've seen PLENTY of brand new CR2032 or CR2025 that were dead in an unopened package.

If that won't do it then your fob itself probably died, is there a local Nissan/Infiniti, or Renault might have the Consult-III software. They would be able to program the new fob, local automotive locksmiths might have the programmer as well so call around.

You should also scan for OBD2 codes, it's probably throwing the NATS lock code.

 

If everything worked before and you just received the weak battery message, you probably installed the battery in the key fob backwards. Flip the battery over and try again.