Why am I receiving "attempt to index nil with 'FindFirstChild'"?

I am receiving "attempt to index nil with 'FindFirstChild'" from two of my scripts, namely ChatHandler and ChangeNameScript, on account of identifying a GUI placed in the player's head by my localscript, Name title giver.

Specifically, I am getting "Workspace.ChatHandler:19: attempt to index nil with 'FindFirstChild'" and "ServerScriptService.ChangeNameScript:8: attempt to index nil with 'FindFirstChild'".

The ChatHandler and ChangeNameScript are supposed to identify the text of the nametag (NameGui.NameLabel.Text) provided by Name title giver, but it does not. The NameLabel, NameGui, and player's head exist at the time in which the scripts go to identify them, however, they don't identify them. I am at my wit's end as to why. I appreciate any response, help, or suggestion. I am new to coding and I am truly lost as to what I am doing wrong. PLEASE tell me if you need any further clarification, I will gladfully provide it. Thank you so much

Below are my scripts and screenshots of my workspace.

https://ibb.co/1Xcmfhv

https://ibb.co/w4pkWS0

Here is my ChatHandler script:

local chatstorage = game.Workspace.ChatStorage
local onChatInputted = game.ReplicatedStorage:WaitForChild("OnChatInputted")

onChatInputted.OnServerEvent:Connect(function(plr, msg)     
    local filteredText
    local filteredString
    local char = plr.Character or plr.CharacterAdded:Wait()
    local Head = char:WaitForChild("Head")  
    local stringval = Instance.new('StringValue', chatstorage)  
    local success, errormsg = pcall(function()          
        filteredText =  game:GetService("TextService"):FilterStringAsync(msg, plr.UserId)           
    end)        
    if success then         
        local success2, errormsg2 = pcall(function()                
            filteredString = filteredText:GetNonChatStringForBroadcastAsync()           
        end)        
        if success2 then                
            local nameGui = Head:FindFirstChild("NameGui")
            local nameLabel = nameGui:FindFirstChild("NameLabel")
            stringval.Name = '['..plr.Team.Name..'] '..nameLabel.Text..': '..string.upper(string.sub(filteredString,1,1))..string.sub(filteredString,2)
            local RS = game:GetService("ReplicatedStorage")
            local Chat = RS:WaitForChild("Chat"):Clone()
            local Bubble = Chat:WaitForChild("Bubble")
            local TextLabel = Bubble:WaitForChild("TextLabel")
            TextLabel.Text = string.upper(string.sub(filteredString,1,1))..string.sub(filteredString,2)
            Chat.Adornee = Head
            Chat.Parent = Head
            if string.len(string.upper(string.sub(filteredString,1,1))..string.sub(filteredString,2))> 15 then game.Debris:AddItem(Chat, 9) else game.Debris:AddItem(Chat, 4) end
        else            
            warn(errormsg2)
            stringval:Destroy()         
        end     
    else            
        warn(errormsg)
        stringval:Destroy()     
    end
end)

Here is my ChangeNameScript:

local remoteEvent = game.ReplicatedStorage.NameChangeEvent

remoteEvent.OnServerEvent:Connect(function(plr, name)   
    local char = plr.Character or plr.CharacterAdded:Wait() 
    local filteredName = game:GetService("TextService"):FilterStringAsync(name, plr.UserId) 
    local filteredNameAsString = filteredName:GetNonChatStringForBroadcastAsync()
    local nameGui = char.Head:FindFirstChild("NameGui") 
    local nameLabel = nameGui:FindFirstChild("NameLabel")   
    nameLabel.Text = filteredNameAsString   
end)

Here is my Name title giver script:

local Players = game:GetService("Players")
local Player = game.Players.LocalPlayer

local Teams = game:GetService("Teams")
local Character = Player.Character

function NameGiver(Player)
    print("Name given: START")
    local nameGui = Instance.new("BillboardGui", Character.Head)    
    nameGui.StudsOffset = Vector3.new(0, 2, 0)      
    nameGui.MaxDistance = 30        
    nameGui.Size = UDim2.new(0, 200, 0, 50)     
    nameGui.Name = "NameGui"            
    local nameLabel = Instance.new("TextLabel")     
    nameLabel.Text = game.Players.LocalPlayer.Name      
    nameLabel.TextStrokeTransparency = 0    
    nameLabel.TextScaled = true     
    nameLabel.Font = "Fantasy"      
    nameLabel.Size = UDim2.new(0, 200, 0, 50)       
    nameLabel.BackgroundTransparency = 1        
    nameLabel.TextColor3 = game.Players.LocalPlayer.TeamColor.Color     
    nameLabel.Name = "NameLabel"
    nameLabel.Parent = nameGui
    print("Name given: FINISHED")
end

-- Manual detection of a property change
local function onChanged(property)
    if property == "Team" then
        print("TEAM CHANGED")
    end
end

-- Connect both events
Player:GetPropertyChangedSignal("Team"):Connect(NameGiver)
Player.Changed:Connect(onChanged)