Why would good rear air shocks not be filling with air to work correctly? on 2001 Buick LeSabre

My rear air shocks were checked and are fine, but are not being activated. What would keep them from being activated and filling with air? How much would it cost to fix this?

Asked by for the 2001 Buick LeSabre
you would need a diag from a shop that can do this work. it runs about 1oo. it could be the leveling sensor or the pump. the diag will give the result and a bid for repairs.