Why won't this rank system work? There are no errors..

so, my friend gave me a rank system and it worked for him but didn't for me, there were no errors outputted, heres the code...

game.Players.PlayerAdded:Connect(function(plr)
	plr.CharacterAdded:Connect(function(char)
		wait(3)
		
		local cTag = game:GetService("ServerStorage"):WaitForChild("Tag"):Clone()
		cTag.Parent = char.Head
		
		cTag.PlrName.Text = plr.Name
		cTag.Rank.Text = "Dumb Newbie"
		
		if plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 0 then
			cTag.Rank.Text = "Dumb Newbie"		
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 3 then
			cTag.Rank.Text = "Smart Newbie"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 5 then
			cTag.Rank.Text = "Average IQ Newbie"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 7 then
			cTag.Rank.Text = "Unaverage IQ Newbie"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 10 then
			cTag.Rank.Text = "Smart Person"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 13 then
			cTag.Rank.Text = "Pretty Smart Person"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 16 then
			cTag.Rank.Text = "Very Smart Person"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 18 then
			cTag.Rank.Text = "High-IQ"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 21 then
			cTag.Rank.Text = "Such Smart, Much IQ"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 24 then
			cTag.Rank.Text = "70% in English Exams"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 28 then
			cTag.Rank.Text = "Insane-IQ"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 47 then
			cTag.Rank.Text = "Albert Einstein"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 67 then
			cTag.Rank.Text = "Unbelievably Smart"
		elseif plr:WaitForChild("leaderstats"):FindFirstChild("Rebirths").Value <= 100 then
			cTag.Rank.Text = "Inf-IQ"			
		end
	end)
end)

I think I know the problem, you haven't made a leaderstats. To do this, you'll need to add a script to the ServerScriptService and copy / paste the following.

game.Players.PlayerAdded:Connect(function(player)
       local leaderstats = Instance.new('Folder', player)
       leaderstats.Name = 'leaderstats'

       local Rebirths = Instance.new('NumberValue', leaderstats)
       Rebirths.Name = 'Rebirths'
       Rebirths.Value = 0
end)

Note: This was from the top of my head, so please don't judge me. Hope this helped you.

Use localscript and put into StarterPlayerScripts, and the Tag from ServerStorage put in ReplicatedStorage. EDIT: https://gyazo.com/95b106c082a78c9787aa898d71a9e5d3

local plr = game.Players.LocalPlayer or game.Players.PlayerAdded:Wait()
local char = plr.Character or plr.CharacterAdded:Wait()
    if char then
        local head = char:WaitForChild("Head")
        if head then
        local cTag = game:GetService("ReplicatedStorage").Tag:Clone()
        cTag.Parent = head

while wait() do
        cTag.PlrName.Text = plr.Name
        if plr:WaitForChild("leaderstats").Rebirths.Value <= 0 then
            cTag.Rank.Text = "Dumb Newbie"      
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 3 then
            cTag.Rank.Text = "Smart Newbie"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 5 then
            cTag.Rank.Text = "Average IQ Newbie"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 7 then
            cTag.Rank.Text = "Unaverage IQ Newbie"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 10 then
            cTag.Rank.Text = "Smart Person"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 13 then
            cTag.Rank.Text = "Pretty Smart Person"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 16 then
            cTag.Rank.Text = "Very Smart Person"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 18 then
            cTag.Rank.Text = "High-IQ"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 21 then
            cTag.Rank.Text = "Such Smart, Much IQ"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 24 then
            cTag.Rank.Text = "70% in English Exams"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 28 then
            cTag.Rank.Text = "Insane-IQ"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 47 then
            cTag.Rank.Text = "Albert Einstein"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 67 then
            cTag.Rank.Text = "Unbelievably Smart"
        elseif plr:WaitForChild("leaderstats").Rebirths.Value <= 100 then
            cTag.Rank.Text = "Inf-IQ"  
		end
        end
    end         
end