It seems the harpoon ability is completely bugged now. When the game launched I don't think there were any problems, but a little while later a patch came out. It seemed the harpoon ability was switched from your pants to your torso chest piece, so anytime you hide the torso chest peace your harpoon would disappear as well. Now after update 1.3.1, the harpoon ability is completely disappeared, so anytime you use it you throw out an invisible harpoon. It does not matter if you have your full armor set on or try and hide some pieces of armor.
Platform: Xbox Series X
Here are some video clips of what's happening
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