So I have an enchant in my list which lets me fortify Archery, except it won't let me enchant this to my Dragonscale Armor. It's just greyed out in the list... Why is this?

Archery can only be enchanted onto different types of armor like gloves, head, necklace, and maybe ring (can't remember). It can't be put on chest or feet.

Certain enchantments can only be on certain pieces.

That makes sense, thanks