ChatMakeSystemMessage not working?

So, I have a script where when a player enters, depending on their rank in a group, a certain chat message is sent. But, of course, it doesn't work :/

IT IS A LOCAL SCRIPT

game.Players.PlayerAdded:connect(function(p)
	if p:GetRankInGroup(2567972) >= 3 and p:GetRankInGroup(2567972) >= 254 then
		game:GetService("StarterGui"):SetCore("ChatMakeSystemMessage",{
			Text = "A member of staff, "..p.Name.." has joined"; 
			Color = Color3.new(51,255,51); 
			Font = Enum.Font.SourceSans; 
			FontSize = Enum.FontSize.Size24; 
		})
	elseif p:GetRankInGroup() >= 1 and p:GetRankInGroup(2567972) <= 2 then
		game:GetService("StarterGui"):SetCore("ChatMakeSystemMessage",{
			Text = "A patient, "..p.Name.." has joined"; 
			Color = Color3.new(51,255,51); 
			Font = Enum.Font.SourceSans; 
			FontSize = Enum.FontSize.Size24; 
		})
	elseif p:GetRankInGroup() == 255 then
		game:GetService("StarterGui"):SetCore("ChatMakeSystemMessage",{
			Text = "The Director, "..p.Name.." has joined"; 
			Color = Color3.new(51,255,51); 
			Font = Enum.Font.SourceSans; 
			FontSize = Enum.FontSize.Size24; 
		})
	else
		game:GetService("StarterGui"):SetCore("ChatMakeSystemMessage",{
			Text = "A guest, "..p.Name.." has joined"; 
			Color = Color3.new(51,255,51); 
			Font = Enum.Font.SourceSans; 
			FontSize = Enum.FontSize.Size24; 
		})
	end
end)

game.Players.PlayerRemoving:connect(function(p)
	if p:GetRankInGroup(2567972) >= 2 and p:GetRankInGroup(2567972) >= 254 then
		game:GetService("StarterGui"):SetCore("ChatMakeSystemMessage",{
			Text = "A member of staff, "..p.Name.." has left"; 
			Color = Color3.new(255,0,0); 
			Font = Enum.Font.SourceSans; 
			FontSize = Enum.FontSize.Size24; 
		})
	elseif p:GetRankInGroup() >= 1 and p:GetRankInGroup(2567972) <= 2 then
		game:GetService("StarterGui"):SetCore("ChatMakeSystemMessage",{
			Text = "A patient, "..p.Name.." has left"; 
			Color = Color3.new(255,0,0); 
			Font = Enum.Font.SourceSans; 
			FontSize = Enum.FontSize.Size24; 
		})
	elseif p:GetRankInGroup() == 255 then
		game:GetService("StarterGui"):SetCore("ChatMakeSystemMessage",{
			Text = "The Director, "..p.Name.." has left"; 
			Color = Color3.new(255,0,0); 
			Font = Enum.Font.SourceSans; 
			FontSize = Enum.FontSize.Size24; 
		})
	else
		game:GetService("StarterGui"):SetCore("ChatMakeSystemMessage",{
			Text = "A guest, "..p.Name.." has left"; 
			Color = Color3.new(255,0,0); 
			Font = Enum.Font.SourceSans; 
			FontSize = Enum.FontSize.Size24; 
		})
	end
end)