Two Bone IK Constraint doesn't always update when the target is moved

I’m trying to get my enemy to hold their gun using animation rigging, instead of messing around with animations.

I have a two bone IK constraint on the enemy’s arm and it’s target is a child of the gun object. The two bone IK constraint updates and readjusts itself when I move the target, but when I move the gun it doesn’t update.

Anyone know a workaround?