A custom made skin pack will not show your skin when used in multiplayer. You are the only person who will be able to see it. For all other players you show up as the last skin you used outside of the skin pack. If you have not changed your skin outside the skin pack you will render as one of the following skins: Steve, Alex, Kai, Efe, Makena, Noor, Ari, Zuri or Sunny. This also seems to happen with custom made skins that are not in skin packs (Ones that are downloaded). My skin does not render towards other players whatsoever and it is really annoying. Before 1.21.50 this was not the case.