Unable to call activity for result?

Goal:
Call method from another activity (dialog) and return result the user chooses

Note: Ive read as many articles as I can on going to other activities, as well as SO posts on this error. I have tried the solutions from about 8 of them and I am just stuck at this point.

Problem:
I am getting the following error:

Ive looked at the manifest, but it doesnt have any of the projects activities so Im not sure why thats even a suggestion. The activity I am calling IS in the CSPROJ file.
I'm also not sure what the HEX part is of the explicit activity class

I get the same error when I try it this way:

Intent intent;
        
if (item is Ph)
{ 
    intent = new Intent(this, typeof(CveActivity));
    intent.PutExtraMItem(item);
    StartActivityForResult(intent, PH_REQUEST_CODE);
}

What Ive tried:

• StartActivity
• StartActivityForResult
• Calling the method of that
  activity
• Instantiating an object and calling the method of that
  activity/class
• Checked that this does exist in the csproj file

Based on the error log, you can try to add Activity tag to your activities(e.g. CveActivity).

    [Activity(Label = "CveActivity")] 
    public class CveActivity : Activity{

     }

I created a demo and achieved this function, you can refer to the following code:

MainActivity.cs

[Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)] 
public class MainActivity : AppCompatActivity
{
    Button button;
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        Xamarin.Essentials.Platform.Init(this, savedInstanceState);
        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.activity_main);

        button = FindViewById<Button>(Resource.Id.button1);
        button.Click += Button_Click;

    }

    private void Button_Click(object sender, System.EventArgs e)
    {
        Intent intent = new Intent(this, typeof(SecondActivity));

        StartActivityForResult(intent, 100);
    }

    protected override void OnActivityResult(int requestCode, [GeneratedEnum] Result resultCode, Intent data)
    {
        base.OnActivityResult(requestCode, resultCode, data);

        if (requestCode == 100) {
            if (resultCode == Result.Ok)
            {
                Toast.MakeText(this,"result is: " + data.GetStringExtra("Test"),ToastLength.Long).Show();
            }
        }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/button1"
        android:text="test"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
</LinearLayout>

SecondActivity.cs

[Activity(Label = "SecondActivity")] 
public class SecondActivity : Activity
{
    Button button;

    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);

        // Create your application here
        SetContentView(Resource.Layout.second_layout);

        button = FindViewById<Button>(Resource.Id.button1);
        button.Click += Button_Click; ;
    }

    private void Button_Click(object sender, EventArgs e)
    {
        var intent = new Intent();
        intent.PutExtra("Test","test");
        SetResult(Result.Ok,intent);
        Finish();
    }
}

second_layout.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
        <Button
        android:id="@+id/button1"
        android:text="return data"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>

StartActivityForResult() is deprecated. Try using registerForActivityResult(). Check the below link for more info
https://developer.android.com/training/basics/intents/result. It might help.

As activity you want to launch is your project's activity, you should register it in the AndroidManifest.xml file (inside application node):

<application ...>
  <activity android:name="your.package.YourActivity" 
          android:exported="true" />
  <!-- all other components -->
</application>