I can't see my golden minecon cape on my skin in customs server

I have the golden cap enable on my skin and then each time I go to a custom server, it just isn't there. I first noticed it when I first went into a server that my friend was making then I decided to test it on other custom servers, and it wasn't just there. Also this was no glitch it kept happening each time I log in Minecraft and join a custom server so I believe it's a bug