Can't Show up skins

Skin can't show up in both server and normal single play mode

What I expected to happen was...:
I expected to see my new skin

What actually happened was...:
Today I just download a new skin for me to use,but when me drop into my friend's server I found out that my skin automatically turn back to Steve and i can't saw my friend's skin too 

Steps to Reproduce:
1. Choose any skin downloaded
2. Start your Minecraft
3. Skin automatically won't show up