Why isn't the Notification Alert appearing?

I have a script in serverscript service where when something spawns, this script fires. It says that the pcall success message is true, but the notification refuses to appear.

--[[-Variables-]]--
repeat wait() until game:IsLoaded() == true
local Remote_Events = game:GetService("ReplicatedStorage"):WaitForChild("#$Remote_Events")
local NotificationAlert = Remote_Events:WaitForChild("NotificationAlert")

--[[Notifications-]]--

NotificationAlert.OnClientEvent:Connect(function(Header, Desc)
	if Header and Desc then
		
		local Callback = function()
			
			print("hello")
		end
		
		local Details = {
			Title = ""..Header;
			Description = ""..Desc;
			Icon = "";
			Duration = 5,
			Callback(),
		
		}
		
		local success, errormessage = pcall(function()
			game:GetService("StarterGui"):SetCore("SendNotification", Details)
		end)
		if success then
			print(success)
		else
			print(errormessage)
		end
		
	end
end)