I was trying to get player heads of existing players using the command

/give @p minecraft:player_head{SkullOwner:"Notch"}

Apparently it only works for players in my LAN eg. Polynomial_ (myself), and my siblings.
However other players such as Notch, Skeppy, ManDooMiN, or any other youtubers doesn't work for me. I'll just get a Steve/Alex player head 

I've even tried to open both my private & public firewall to minecraft, and tried the commands on the other device under the same LAN but it still doesn't work. 

No mods are used.