how can i fix my central locking or is there a fuse for central locking?

simply i had my battery in my keys changed as i thought they wee flat however the central locking isnt working of key remote worked finr until yesterday if put key in door and turn all doors unlock and lock but when prss key/remote the blinker lights dont flash and the car wont unlock or lock therefore i was wondeeing if it just a relay or fuse thanks