In the realm of magic, I am the ultimate offender.
Trying to Transmute an item
when you have both items in the transmutation window, click on the items icon you want the look from, and the stat you want to keep.
A couple things. First, make sure you have unequipped both items. Second, make sure you have selected ALL of the boxes so they line up in the middle – the one you want the looks of; the stats; and any bonuses – all three must be selected before you get the lighted transmute button.