The actual "Put Armor on and see it" part was removed years ago on every armor except EV Suits (wich still show when you "activate" em). Instead ALL old non rep. armor options should now be in the Tailor. For rep armor its like eliteempire already told you -> collect the whole set and get a Tailor unlock for the visuals.
Same for me.. Cant modify some ships like the commander rank escort/cruiser or the Ambassador while others like the Samsar, pilot Escort and Xindi Carrier work fine.