My skins are not loading in correctly.

What i expected to happen was for my skin to load in as a Slim Model and the skin I chose.

What actually happened was my skin was the model I ended up having was a classic. When I tried changing it again to a different skin it wouldn't.

Steps to Reproduce:
1. Changing the skin before you play.
2. Load into any server or world.
3. skin doesn't pop up as the slim model/ It won't change back to the skin you chose either.