attempt to concatenate Instance with string line 11?

game.Players.PlayerAdded:Connect(function(player)
    player.Chatted:Connect(function(Message)
        local SplitMessage = Message:split(" ")
        if SplitMessage[1] == "/rank" then
            print("Command Is Correct")
            local NameOfPlayerToGiveRankTo = SplitMessage[2]
            local PlayerToGiveRankTo = game.Players:FindFirstChild(NameOfPlayerToGiveRankTo)
            local RankName = Message:split(NameOfPlayerToGiveRankTo)[2]

            PlayerToGiveRankTo.leaderstats.Rank.Value = RankName
            print(player.Name.." changed "..PlayerToGiveRankTo.."'s rank to "..RankName.."!")
        end
    end)
end)

This is the client side notification

EventsFolder.NotifySender.OnClientEvent:Connect(function(PlayerToGiveRankTo, RankName)
    wait(0.5)
    game.StarterGui:SetCore("ChatMakeSystemMessage",{
        Text = "You have changed ".. PlayerToGiveRankTo .."'s rank to ".. RankName .."!";
        Font = Enum.Font.SourceSansBold;
        Color = Color3.fromRGB(85,255,0);
        TextSize = 18;
    })
end)