Help with first hunting mission, using the bow.

[Fat gorilla]

Why does the bow not shoot when the crosshair is red? At the start of the level I practiced on a tree with all the arrows, I understand how the bow works. This is not a stamina issue. When I am in good range of a deer, I draw the bow back, aim on the deer, the dot is red, I release the shot and nothing happens. The arrow doesn't fire. I repeat the same process not aiming on a deer and the bow fires. Please help me this is so frustrating.