Shadowmourne bugged

I've been having this problem for a while now and have been finding a way around it, but now I can't. I just bought Shadowmourne and the item icon comes up as a red question mark and it says it's not a "valid target" when I try to enchant it. It also won't let me attack with it because it says I have no item equipped. This is also the case with my Medallion of the Horde trinket but for that I was able to create a macro /use 13 to use it. A few other items will come up with the red question mark icon from time to time but none have been as significant as this. Is there something wrong with the client I downloaded or is this an easy fix?

Try opening a ticket in-game and explain your issue.

did you try to delete "Cache" folder? You can find it inside your WoW folder

Btw, are you playing with WoW for windows or for Mac?