BepInEx plugin loaded, but HarmonyPatch annotation have no effect

[CannonFodderEX]

This is my first time using BepInEx.
I'm trying to write a plugin for game Metal Unit.
The plugin is successfully loaded, but no harmony patch works.

I created my project with command line:
dotnet new bepinex5plugin -n MetalUnitCheatPlugin -T net46 -U 2018.4.9

I've gone through troubleshooting page and did all I can,
https://docs.bepinex.dev/articles/user_guide/troubleshooting.html

I wrote another plugin for game Smelter just for test, same problem.

I can confirm I'm not patching wrong method, because I tested by modify the same method in Assembly-CSharp.dll with dnspy.

Console Log:

[Message: BepInEx] BepInEx 5.4.21.0 - MetalUnit (2021/1/28 10:40:42)
[Info : BepInEx] Running under Unity v2018.4.9.13252388
[Info : BepInEx] CLR runtime version: 4.0.30319.42000
[Info : BepInEx] Supports SRE: True
[Info : BepInEx] System platform: Bits64, Windows
[Message: BepInEx] Preloader started
[Info : BepInEx] Loaded 1 patcher method from [BepInEx.Preloader 5.4.21.0]
[Info : BepInEx] 1 patcher plugin loaded
[Info : BepInEx] Patching [UnityEngine.CoreModule] with [BepInEx.Chainloader]
[Message: BepInEx] Preloader finished
[Message: BepInEx] Chainloader ready
[Message: BepInEx] Chainloader started
[Info : BepInEx] 1 plugins to load
[Info : BepInEx] Loading [MetalUnitCheatPlugin 1.0.0]
[Info :MetalUnitCheatPlugin] Plugin MetalUnitCheatPlugin is loaded!
[Message: BepInEx] Chainloader startup complete
[Info : Console] Searching for compatible XInput library...
[Info : Console] Found Xinput1_4.dll.
[Info : Unity Log] Loaded strings - 1.tsv with 2756 entries.

The original method looks like this:

public void OnDiscordClick()
{
Application.OpenURL("some url");
}

My plugin code is very simple, as below. I'm patching menu button function because it's easy to test.

using BepInEx;
using BepInEx.Logging;
using HarmonyLib;
using UnityEngine;

namespace MetalUnitCheatPlugin
{

[BepInPlugin(PluginInfo.PLUGIN_GUID, PluginInfo.PLUGIN_NAME, PluginInfo.PLUGIN_VERSION)]
public class Plugin : BaseUnityPlugin
{
    internal static new ManualLogSource Log;
    private static readonly Harmony Harmony = new Harmony("MetalUnitCheatPlugin");

    private void Awake()
    {
        // Plugin startup logic
        Plugin.Harmony.PatchAll(System.Reflection.Assembly.GetExecutingAssembly());
        Logger.LogInfo($"Plugin {PluginInfo.PLUGIN_GUID} is loaded!");
        Log = base.Logger;
    }

    [HarmonyPrefix]
    [HarmonyPatch(typeof(TitleMenuController), nameof(TitleMenuController.OnDiscordClick)/*"OnDiscordClick"*/)]
    static bool OnDiscordClickPrefix()
    {
        Debug.Log("TitleMenuController:OnDiscordClick:Prefix:LogTest");//Unity Log
        Log.LogInfo("TitleMenuController:OnDiscordClick:Prefix:LogTest");//BepInEx Log
        FileLog.Log("TitleMenuController:OnDiscordClick:Prefix:LogTest");//Harmony Log
        return false;
    }
}

}

None of the logs recorded my message, and the original method is still executed. So I guess the prefix is not called.

I've no idea what's wrong, and no direction of determin the cause of problem.

Please help.

Update1:
I added

I looked into some plugins written by others, one of them calls "new Harmony()" in Awake(). I added similar code in my plugin, and the patch worked!

new Harmony("MetalUnitCheatPlugin").Patch(AccessTools.Method(typeof(TitleMenuController), nameof(TitleMenuController.OnDiscordClick), null, null), new HarmonyMethod(AccessTools.Method(typeof(Plugin), nameof(Plugin.OnDiscordClickPrefix), null, null)), null, null, null, null);

It seems the problem is [HarmonyPatch(typeof(TitleMenuController), nameof(TitleMenuController.OnDiscordClick)/"OnDiscordClick"/)] annotation have no effect.
Why? Is this an issue?

[CannonFodderEX]

Please ignore this question.
I've figured out I need another class for annotations.