making a GUI

[mhnn]

command /mines:
  trigger:
    open chest inventory with size 3 named "&6Mining Locations":
      format gui slot 0 with player's head named "&2Earth's Mines":
        on click:
          # Actions for Earth's Mines menu
          close player's inventory
          send "&aClosed Earth's Mines menu."
      format gui slot 1 with player's head named "&4Nether's Mines":
        on click:
          # Actions for Nether's Mines menu
          close player's inventory
          send "&aClosed Nether's Mines menu."
      format gui slot 2 with player's head named "&5End's Mines":
        on click:
          # Actions for End's Mines menu
          close player's inventory
          send "&aClosed End's Mines menu."
      format gui slot 3 with player's head named "&0Void Mine":
        on click:
          # Actions for Void Mine menu
          close player's inventory
          send "&aClosed Void Mine menu."
      format gui slot 26 with paper named "&7Close":
        on click:
          close player's inventory
          send "&7Closed the Mining Locations menu."
 

it just does not work