»How do i change my skin!

Hey guys im a premium minecraft user here,And i join a cracked sever which is guildcraft so i wan my own premium skin back,How do i do it?How do i change my skin back to my premium skin?My own wan that i had already before i came to the cracked sever.My ingame name is - ItsBeth

 

Type /skin update in lobby,if you're a premium player.

 

That command isn't working for me.
Just says "You must be a premium player to use this command.
(I am a Premium Player)

 

the premium skin command is a bit buggy rn, alot of people have reported it has a glitch/bug