Not able to save skins to library.

So I was working on a server of mine and I was trying to add skins to my NPCs. I uploaded a skin saved on my phone to my account via the Minecraft website. I went on the launcher to add the skin to my library, but I couldn't. There was an error saying "Unable to duplicate skin". This same error kept showing up any time I wanted to create or duplicate a skin, each error changing to what I was trying to do. I am unsure of why this happened, but I'm pretty sure it started after an update for the launcher.