Purchasing Items after Rebirth?

I believe your MyDebounce never reverts to true. In this case, it only is able to run it once since the dbounce never reverts back to true and it's required to be true for the function to run.

Also, since the MyDebounce doesn't seem to be local in the function, if one player fires the event, the MyDebounce will change for all players. You want to make the MyDebounce local to the function.

local MyDebounce = true then put the rest of your script

ReplicatedStorage.ShopEvents.Ninjago.OnServerEvent:Connect(function(player)
local MyDebounce = true 
    if player.leaderstats.Money.Value >= 500 and MyDebounce == true and player then
        MyDebounce = false
        player.leaderstats.Money.Value = player.leaderstats.Money.Value - 500

        ServerStorage.Tools.AzureSword:Clone().Parent = player.Backpack
        game.StarterGui.Shop.Shop.BuyingInfo.LegoNinjago.Buy.Text = "Bought"

        if player.leaderstats.Rebirths.Value >= player.leaderstats.Rebirths.Value + 1 and MyDebounce == false and player then
            MyDebounce = true

        end
    end
end)