Helloooooo

You need to put %attacker's uuid% instead of %player's uuid%, because in the event you are calling (on death) there are no players but an attacker and a victim.

you should use skript-gui, here is an example of how you can use it: function gui(p: player): create a gui with virtual chest named "&cGui" with 3 rows: make gui slot (integers between 0 and 26) to gray stained glass pane named "" make gui slot 4 to shiny emerald named "&aTest": send "&aThis will be sent to the player upon clicking the emerald" to {_p} open last gui to {_p}

youtube, forums, docs and by watching others skripts and trying to remake them myself