Anyone know how to do this

The fob battery works as the light comes on the fob when a button is pressed but it won't open and lock the car. I've read so many posts and seen videos but it just won't work

I have only one key with the built in lock and unlock button.

I follow the guide which says out key in ignition and turn key until the lights come on and remove key after 5 secs. Then press and hold lock button and at same time press unlock 3 times


Nothing works please help