I have a 1.12.2 server with magma and I have around 70 mods. I can see the wings in the wardrobe but later in the skin, doesn't appear, and the others can't see either.

Here you have the screenshots

I don't know how to solve this. If you want, I could say you which mods are in the mod pack.

I would like to fix it as soon as possible

Sorry, 1.7/1.12 is no longer supported