my code redemption system can only redeem one code, help?

In short, Why put it else statement when the code isnt directly relating to the subject.

Remove the else statement and change the script like this:

game.ReplicatedStorage.cd.OnServerEvent:Connect(function(player,code)
    local ss = game:GetService("ServerStorage")
    local reward = ss:FindFirstChild("PlayerMoney")
    local r = reward:FindFirstChild(player.Name)
    local key = "codes-"..player.userId
    if code == "code1"  then
    if player.Codes:FindFirstChild(code) == nil then
    local bool = Instance.new("BoolValue")
    bool.Parent = player:FindFirstChild("Codes")
    bool.Name = code
    r.Value = r.Value + 500
end
end
    if code == "code2"  then
    if player.Codes:FindFirstChild(code) == nil then
    local bool = Instance.new("BoolValue")
    bool.Parent = player:FindFirstChild("Codes")
    bool.Name = code
    r.Value = r.Value + 500
    end
    end
end)