the skintones I was trying to use were defaults that were broken with previous patches. Just replying to my own thread with part of the solution that was posted previously. Everything else is the same so you only need this if you need skins enabled for Aliens, Vampires, or Spellcasters. Added options to enable skintones for all occults. Changed default skintone category to Miscellaneous. Switched to a better color conversion for burned skin textures, which makes the skin look redder (or greener or bluer) when burned. S4pi library for package and image handling. How to convert skintones manually using Sims4Studio: This is really quick and dirty so keep copies of your original skintone packages and please report errors. Your system may report the process as not responding but it should complete eventually. Straight conversion is fast, but if you're adding tan and burn textures and there are more than a few skintones in the package it'll take a seriously long time to compress the files and save after converting. It uses the swatch color to judge how light/dark the skin is and decide which color(s) are dominant for fantasy skins, so an accurate swatch is important. It makes fairly accurate textures for natural skin colors and makes its best guess at tan and burn colors for fantasy skins. It sets up the light/dark slider with standard values. Pick which skintone panel you want the CC skins to appear in and this tool will convert them. Then remove the old package from your Mods folder and replace it with the converted one.

When running this tool, do NOT save the converted package over the original that may corrupt the package and you could end up with an unusable file! Give it a new name or save it in a different location. If you see a message saying there are no tones found in the package, you're probably trying to convert one of those. It is also NOT for texture-only default replacements. This tool is ONLY for skin colors that are applied in the skintone panel in CAS, NOT 'skintones' that are applied in skin details. This tool will update them and optionally will add tanned and burned textures to older skintones. With the December 2020 patch, CC skintones stopped appearing in the CAS skintone picker.

Sims 4 melanin pack update patch