Why doesn't this work?

[scenic harbor]

You didn't define what's the player

[warped egret]

@onyx mason
what is your current manifest version

it should look like that

maybe try this code

world.beforeEvents.chatSend.subscribe((data) => {
    const player = data.sender
    const message = data.message
    const rank = player.getTags().find(tag => tag.startsWith("rank:"))?.replace("rank:", " ") ?? ""
    world.sendMessage(`${player.name}${rank} §l» §r${message}`)
    data.cancel = true
})