stoves panache 600sl?

Hi, I have a stoves panache 600sl cooker and 2 bits of the control knobs have broken off. I have got some new ones but, they don,t seem to fit properly even though they are the proper ones for this oven. My problem is when I try to put the control knob on the part where it is suppose to attach to so that it turns the gas off when I put the lid down are at the other side. I don,t understand why this is as all the control knobs are exactly the same there is no right and left. Can anyone help me please I am obviously doing something wrong as I was told they just slide on. Regards