Can't enchant heirlooms?

Hey all, Im on Lordaeron and I have both the shoulders, and the PvP gun. I tried enchanting my shoulders, but i figured that wouldn't work, but I tried putting a scope on my gun, and it also says invalid item. Is there enchant prevention on this server? I am quite confused, and would appreciate any help. Thank you!

only enchants with NO level requirement will work on heirlooms. Also shoulder enchants will make heirlooms soul bound afaik.

Ah okay, Its the level requirement that does it. Thanks so much man, helped me a ton.