Hey, I tried your code and it seemed to work perfectly fine for me.
Make sure that the code is as high as it can be in the script and not under any statements that may yield further instructions (example: if you have a while true do statement above this code then it wouldn’t work.
Also, make sure you’re using a localscript and not a serverscript. To read more about Server Scripts vs Local Scripts there is a thread here: LocalScript vs. Script help
Finally, make sure your code is in a locally replicated area. The most common being StarterGui and StarterPlayerScripts.
If you’re still having issues I’ve re-formatted the code along with sent a place file containing just the code.
Code
local StarterGui = game:GetService("StarterGui");
StarterGui:SetCore("ChatMakeSystemMessage", {
Text = "{System} Welcome to Sprint Course!";
Font = Enum.Font.Cartoon;
Color = Color3.new(253, 251, 255);
FontSize = Enum.FontSize.Size96
})
Place File: Chat-Notification.rbxl (18.1 KB)