The chameleon tongue is a complicated apparatus. It requires coordination with the eyes for precision aiming and then an incredible firing of the tongue out to hit the prey. There are a number of things which can affect the tongue function. The two main issues that chameleon hobbyists run into are 1) Metabolic Bone Disease and 2) vitamin A deficiency.
Metabolic Bone Disease (MBD) is caused by a lack of calcium in the bones to make them rigid and strong. Thus the jaw can warp. As the mouth is the launching platform for the tongue any deformity will make accurate shooting difficult. Your chameleon will try and shoot and may miss if the deformity is beyond what the chameleon’s brain can compensate for.
Vitamin A deficiency can affect the tongue’s use by degrading the eye sight. If the eyes are crusted over and have difficulty aiming then the tongue use will suffer.
The chameleon will shoot the tongue and either miss or else the tongue will not extend all the way to the prey.
Eventually, the chameleon will not even try to shoot the tongue.
The most important thing in treating a tongue issue is to determine where the problem is. This is best done with the help of a competent veterinarian.