Dotfuscator Error while trying to build a .Net Core console app

Question

I have a simple .Net Core console app and am trying to obfuscate the generated dll using Dotfuscator Community tool https://www.preemptive.com/dotfuscator/ce/docs/help/index.html:

 class Program
    {
        public static void Main()
        {
            Console.Write("\n\nFunction to calculate the sum of two numbers :\n");
            Console.Write("--------------------------------------------------\n");
            Console.Write("Enter a number: ");
            int n1 = Convert.ToInt32(Console.ReadLine());
            Console.Write("Enter another number: ");
            int n2 = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("\nThe sum of two numbers is : {0} \n", Sum(n1, n2));
            Console.ReadKey();
        }

        public static int Sum(int num1, int num2)
        {
            int total;
            total = num1 + num2;
            return total;
        }
    }

After choosing the generated dll from the Add Input option, when I try to build it using the Build option, I get Build Error(screenshot below) although the program builds successfully in my local.

Apparently, from the error, it seemed that System.Runtime inside the bin -> Debug -> netcoreapp3.1 folder is missing; so I installed it in my application, but the error still persists.

My .csproj file:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <SignAssembly>false</SignAssembly>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Obfuscar" Version="2.2.28">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <PackageReference Include="System.Runtime" Version="4.3.1" />
  </ItemGroup>

</Project>