As long as you are allowed to equip that certain piece of gear you want to transmog to AND it is not soulbound, it should work. Otherwise you have to get a new copy of that piece of gear to use its looks.
Had same issue, only got it to work again by deleting the files inside the following folders: .patch cache and prepatch. These are found at Users\Public\Games\Cryptic Studios\Neverwinter\Live or wherever you selected to install Neverwinter to. Had to do a 3mb patch again when i launched the game, and all prepatch data was…