Error: FireAllCients is not a valid member of RemoteEvent?

Hi all, just had an error that I've tried but failed to resolve.

I'm trying to create an announcement system for a small group game, and I repeatedly receive the error: "FireAllCients is not a valid member of RemoteEvent"

I've tried very little as not much has come to mind, any ideas would be appreciated.

Local script:

local repStore = game:GetService("ReplicatedStorage")
local gui = script.Parent
repStore.sendAnnouncement.OnClientEvent:Connect(function(msg,timer)
    gui.MainFrame.Visible = true
    gui.MainFrame.Background.Message.Text = msg
    wait(timer)
    gui.MainFrame.Visible = false
end)

Server Script:

local repStore = game:GetService("ReplicatedStorage")
local sendAnn = repStore:WaitForChild("sendAnnouncement")

local message = "wag1"
local timer = 5
sendAnn:FireAllCients(message,timer)