Custom Npc Skins Error

[AbsoluteLeonidas]

Alright, I am on version 1.12.2 I am working on a server. I am using custom skins in the skins folder in my custom npc files. It comes out a black and purple. Mind you theses skins are hd, but I tried the regular 64x64 resolution and still nothing. I do hope someone gives me some in sight on a solution or the modded, Noppes, can help me. I’ve seen other people have this problem too, but I can’t figure a way around it though, please help.