Cps is not a valid member of Player?

I have a couple of suggestions. Feel free to completely disregard what i'm saying if you disagree....

If you'd like things to not show up under leaderboards, you can always just add a folder within the leaderstats folder or whatever it is...

This creates a leaderstats & a hidden folder

leaderstats are under player and hidden is under the leaderstats

The cool part is... Only values under leaderstats will show.. Therefor you won't see 'Hidden' in the players leaderstats

local Players = game:GetService('Players')

Players.PlayerAdded:Connect(function(player)
	local leaderstats = Instance.new('Folder')
	leaderstats.Name = 'leaderstats'
	
	local NonHidden = Instance.new('NumberValue')
	NonHidden.Name = 'NonHidden'
	NonHidden.Value = 5
	NonHidden.Parent = leaderstats
	
	local hidden = Instance.new('Folder')
	hidden.Name = 'Hidden'
	
	local HiddenValue = Instance.new('NumberValue')
	HiddenValue.Name = 'HiddenValue'
	HiddenValue.Value = 500
	HiddenValue.Parent = hidden
	
	hidden.Parent = leaderstats
	leaderstats.Parent = player
end)

click this link to see the outcome of this script

the value is still going to be there although it's now hidden..

Anyways

You're not really giving enough information for us to be able to give you reliable information.

I don't know how you have your scripts set up with the leaderstats and things.. But I redid the code you gave with what I mentioned above..

I don't expect you to copy... But I do expect you to read over and learn why I did what I did.

I also have a bunch of if statements making sure things don't end up being nil, if they are then it won't cause an error, it'll just print what the issue was..

local Players = game:GetService('Players')

local function AddTickets(player,stats)
	local leaderstats = stats ~= nil and stats or player:FindFirstChild('leaderstats')
	if leaderstats then
		local hidden = leaderstats:FindFirstChild('Hidden')
		if hidden then
			local Tickets = leaderstats:FindFirstChild('Tickets')
			local Cps = hidden:FindFirstChild('Cps')
			if Tickets and Cps then
				while true do
					leaderstats.Tickets.Value = leaderstats.Tickets.Value + hidden.Cps.Value
					wait(1)
				end
			elseif Tickets == nil then
				print('Tickets was not found under leaderstats')
			elseif Cps == nil then
				print('CPS was not found under hidden')
			end
		else
			print('Hidden was not found under',player)
		end
	else
		print('leaderstats were not found under',player)
	end
end

Players.PlayerAdded:Connect(function(player)
	local leaderstats = Instance.new('Folder')
	leaderstats.Name = 'leaderstats'
	
	local Tickets = Instance.new('NumberValue')
	Tickets.Name = 'Tickets'
	--Tickets.Value = 5
	Tickets.Parent = leaderstats
	
	local Rebirths = Instance.new('NumberValue')
	Rebirths.Name = 'Rebirths'
	Rebirths.Parent = leaderstats
	
	local hidden = Instance.new('Folder')
	hidden.Name = 'Hidden'
	
	local cps = Instance.new('NumberValue')
	cps.Name = 'Cps'
	cps.Value = 1 -- whatever the starting value is
	cps.Parent = hidden
	
	hidden.Parent = leaderstats
	leaderstats.Parent = player
	AddTickets(player)
end)

If you have any questions at all, feel free to comment on this.