I'm having problems loading my minecraft skin?

I just recently created my skin via Minersneedcoolshoes.com. I downloaded it from the website onto my computer, and uploaded it to my profile on minecraft.net. Whenever I go into a multiplayer server (Mineplex) my skin hasn't seem to have loaded, and is all black. After a while I just rested my skin to Steve, which loaded perfectly fine. I tried to upload a pre-made skin, to see if the problem was the skin itself, but that also didn't load. Can you please help me diagnose the problem and find a solution?