Playing sport all together and my ankles have begun to crack all of the time, why could this be?

A few reasons: Ligamentous laxity, decreased joint space between the bones, previous injury...Hard to say definitively. However, at 40 years old, you have to remember hormonal changes occurring can create laxity in the ankle support ligaments. This is the most plausible reason. Continue workouts, but pay attention specific areas that are achy. If still concerned, see a foot ankle specialist for evaluation.