I have a hypothesis that prior to booting up the latest version of Minecraft, I was able to upload 2 skins to the library without any issues, then when I was done setting up a modded version sometime later, it doesn't allow me anymore. Even the specifications of the skin fits the criteria of the error, I have checked the dimensions and data to see that there is no issues at all. Which is strange on its own

1. I have restarted Minecraft, which doesn't work at all. Like opening and closing the window.
2. This includes logging in and out, doesn't work
3. I have tried on different computers, still doesn't work. 
4. Reuploading the same skins that successfully uploaded to the library, it didn't upload!

Below are attached images of the two skins I was able to successfully upload and the error message