Complete Arsenal Weapon

I am trying to switch my Barbarian from Rend to Whirlwind, but it won’t let me. It says that I need “any complete arsenal weapon.” What is a complete arsenal weapon?

“Complete arsenal weapon” should mean any equipped weapon. Maybe WW doesn’t have a weapon assigned (but idk how that could happen)? If you point to the skill in your bar, at the bottom of the tooltip it should show assigned weapon.

Do you have a weapon slot unequipped?

Do you have all 4 weapons slots equipped? The arsenal system barbs having 4 weapons when other classes don’t. Fun fact the arsenal system causes more tears the peeling onions do!

I have all four weapons slots filled. However, one of them is yellow while the others are gold. I exited the game and even shut down my computer, but when I went back on, it still would not let me use the Whirlwind skill.