In it you will find a program called SkinConverterSheep.
You can use it to convert.
But if it still doesnt work, then its not your format.
Its the skin names.
You cant use LARGE letters or numbers in your skin names.
So rename them.
Thanks for your reply. I am going to have a look at it.
Guess I need to convert 1.8 skins back to 1.7.
I am currently using custom npc's for 1.12.2 and this version doesn't seem to support 1.8+ skins at all. The only thing I see is an empty skin model. The 32x64 skin model in the selection doesnt seem to do anything either.