I need help with a currency script? And apparently this title isn't specific?

this is due to the difference between studio and the actual game, in studio, the game preloads assets and loads fairly quickly, but in an actual game, there is a fair bit of latency, meaning that the local script that waits for the event "cow" waited a substantial amount of time for the event "cow". Although this is only part of the explanation. The other part is that you never established a maximum wait time, which means that if the event "cow" doesn't exist, the script would never go beyond waiting for the event "cow" and never run any other code. To combat this, you can set a maximum wait time on the WaitForChild() function.

local plr = game.Players.LocalPlayer
local h
plr:WaitForChild("Events",60):WaitForChild("cow",60).OnClientEvent:Connect(function()
    local v = plr:WaitForChild("PlayerData",60):WaitForChild("cowss",60)
    v.Value = v.Value + 10
    local t = plr:WaitForChild("cows",60).Frame.s
    t.Text = v.Value
end)

Notes to take away

--WaitForChild() waits forever if no maximum wait time is set
--connect is deprecated, the use of Connect is now preferred
--[[if you repeatedly use something like game.Players.LocalPlayer, make a variable for that, 
then use that variable]]

As long as you provide the code and give a general idea of what it's supposed to do, one of us here on SH will gladly help you.

Anyways, you have alot of messy code that you can fix and it'll help you become better at knowing what you're doing.

Your main issue is how you're going about using the Server to Client communication to update the player interface. I'm going to give you a run down of how it should look like and hopefully you can reformat your old code to how it should be.

We'll start with using a Script inside of the part that will be clicked. Make sure you have a remote event inside ReplicatedStorage, and a part in workspace with a click detector inside it.

Script inside part:

--Define ReplicateStorage
local RS = game:GetService("ReplicatedStorage")
--Define the remote event in RS
local event = RS:WaitForChild("RemoteEvent")

--ClickDetector inside our part
local clickDetector = script.Parent:WaitForChild("ClickDetector")

--When the player clicks our part: the server will tell the client to "addPoint"
clickDetector.MouseClick:Connect(function(playerThatClicked)
    event:FireClient(playerThatClicked, "addPoint")

    --Not sure whether you need to add a point to the player's leaderstats
    --If you do, you can still do it in here since we're in server side
end)

Now we'll insert a local script inside a ScreenGui that can be inside of StarterGui. That way the player spawns with the GUI every time. I'm going to use a TextLabel in ScreenGui to show our points. Our points will be added in an IntValue that we can insert inside the ScreenGui.

Local Script inside a ScreenGui:

--Define ReplicateStorage
local RS = game:GetService("ReplicatedStorage")
--Define the remote event in RS
local event = RS:WaitForChild("RemoteEvent")
--Find our textlabel
local gui = script.Parent
local textLabel = gui:WaitForChild("TextLabel")

--Find our intvalue inside ScreenGui
local points = gui:WaitForChild("IntValue")

--Use a Changed event on points (IntValue) to change our TextLabel's text
points.Changed:Connect(function(property)
    textLabel.Text = property
end)

--When our remote event is triggered, check the reason and add a point to 'points'
event.OnClientEvent:Connect(function(reason)
    if reason == "addPoint" then
        points.Value = points.Value + 1
    end
end)

Notice that FireClient() takes a player parameter followed by any arguments after that. I'm using an argument of type string value to pass a sort of "Reason" that my client looks out for. If my local script notices the reason is "addPoint" then we'll run the code under it. That way we can reuse the remote event to tell the client to do other things. Like taking away some points.

If somethings wrong with any of my code or you need further explanation let me know.

edit: formatting