I'm playing the latest version of 1.12.2 Dalek Mod. And I was doing some testing before going to a survival world, and when I opened River's Diary the option "Change Skin" is grayed out. Help please?

Here's a screenshot:

This feature was disabled in the latest 1.12.2 update. Everyone has it.
It's because the code wasn't very efficiently written, no one knew what was going on, and it was straining multiplayer servers a bit.