Can't upgrade tomahawk in Mob of the Dead

[Lalo Enjoyer]

As the title says, I tried upgrading the tomahawk with a friend in a match and then with two friends in another match, and it doesn't upgrade. Any steps that I'm missing? We spend a lot of rounds on the bridge killing only with the tomahawk and still nothing, no sound, and when we throw it on the fire pit, it still comes back.

[stikyfingers]

Lalo Enjoyer me too