I can use every hair when I use the "items" section in the wardrobe. But I can't use any redeemed wig using the hair tab, it won't show up, regardless how many times I click the "show on avatar"-button... What should I do? A friend of mine has the same problem.

Do you have the hair layer above the base layer? If you have a wig on over the hair layer unless you remove it you won't be able to see it either.

omg, thank you, that solved it <3