Hello, not long ago I created my own menu on my server. But I ran into an incomprehensible problem, my plugin is working (normal for 3 lines to check) and the menu UI does not appear on the screen

using Oxide.Game.Rust.Cui;

namespace Oxide.Plugins
{
    [Info("Menu Start", "NiceGame", "0.0.1")]
    class  MenuStart : RustPlugin
    {

    void OnEntityTakeDamage(BaseCombatEntity entity, HitInfo info)
    {
        var player = info.InitiatorPlayer;
        if (player && player.IsAlive())
        {
            NextTick(() =>
            {
                if (entity.IsAlive())
                {
                    string json = CUI_MAIN;
                    CuiHelper.AddUi(player, json);
                    Puts("Работает!");
                }



            });
        }
    }
    [ChatCommand("menu")]

    void ChatCommandmenu (BasePlayer player)
    {
                    string json = CUI_MAIN;
                    CuiHelper.AddUi(player, json);
                    Puts("Работает!");
    }
  const string CUI_MAIN = @"

{
  ""menu"": [
    {
      ""name"": ""menu_bg"",
      ""parent"": ""Overlay"",
      ""components"": [
        {
          ""type"": ""RectTransform"",
          ""anchormin"": ""0.06 0"",
          ""anchormax"": ""0.06 0"",
          ""offsetmin"": ""-43 43"",
          ""offsetmax"": ""86 70""
        },
        {
        ""type"": ""UnityEngine.UI.Image"",
        ""sprite"":""Assets/Icons/rust.png"",
        ""color"": ""0.5254902 0.5254902 0.5254902 0.2980392""
        }
      ]
    }
  ]
}
     
        ";


    }
   
}

I thing your text JSon is problem. Do you use Rust Cui Generator? Try to change all double quote to only one.
""name"": ""menu_bg"",   >>  "name": "menu_bg",

Yes, I use a generator, and always replace "" with double