I recently completely uninstalled and reinstalled minecraft after cleaning up my computer a bit. When I joined a multiplayer server, all player skins, npc skins, custom head skins, etc. were reset to steve/alex heads and skins.

I did some research and found that the problem was the skins folder in minecraft's assets folder. Usually every skin that you see is stored in this folder. The minecraft Application Support folder was deleted because of the uninstall, but after reinstalling, there was no skins folder created in Application Support/minecraft/assets. A screenshot of the contents of the assets folder is attached, as well as an example of the problem.

I manually created a skins folder in assets, but even after that nothing was saved there. I've tried relogging into the server, restarting minecraft, and restarting my computer but nothing is making the skins show up.