Why Does My Ionic Breeze Seem To Be Losing It’s Effectiveness At Eliminating Odors?

I've had my two ionic breezes for over 2 years now and even though they still capture airborn particles the smell is increasingly bad by the catbox - it used to work better. I tilt it up and down several times to reactive it like I've been encouraged to do but the smell is not getting better and it's sitting inches away from the litter box? The small one in the bathroom got better after I tilted it up and down to make the inner compartments move up and down several times. Ideas?