Why will this "Changed" event not function?

I've been working on a game that heavily relies on mouse input these past few days, and have hit a snare nearly immediately. I'm making a "tool" of sorts that works without being in a tool, but is just a localscript that is placed into StarterPack.

I've done a few tests, and local scripts do run correctly whilst in the backpack. However, this particular script isn't working out for me, and I don't see why it isn't --

mouse.Changed:connect(function(property)
    print("Changed!")
    if property == "Target" and mouse.Target then
        print("CheckWorked")
        Empty(mouse.Target);
    end
end);

function Empty(target)
    print("Empty")
end

I'll make it easy to tell how much is working... none of the prints even go off whenever I mouse over a brick. I've tried placing the script into StarterGui as well, to no avail.

Thank you for reading, and I hope to find a solution!