Remove the scope from the rifle. Set the scope on the lowest magnification setting. Stand the scope on a hand mirror. You should see two reticles, one is the reticle and the other a reflection. Adjust the reticle until it is is over the image. If the adjustment is broken it won't track. If it does track, once the image and the reticle are together hold the rear bell in your hand and whack the front bell into the open palm of your other hand and see if the reticle has moved. If the reticle moves every time you apply the lateral shock to the scope after you recenter the scope it's not holding zero.
