Niagra System Animation Issue

I have animated the curtain being burnt gradually and want the fire to do the same ( i.e. want the fire to go up in the z-axis gradually).

I added Box Location and then to animate the Box Offset for Z-Axis, I added a float from curve to the z-axis and added keyframes to the curve but it is not Animating. How to tackle this?

(There are two keyframes in the curve when changing the location of the first keyframe the fire changes its location on the z-axis, but when changing the location of the second keyframe the fire remains at the same place)