ServiceStack 3.9.* to 4.*

I am trying to change ServiceStack in my service from 3.9.43 to 4.0.9.

I had to change several things in my code and mostly followed the release notes for this.

There were a couple of weird things for me, like not finding anything to replace ServiceStack.WebHost.Endpoints or AppHostHttpListenerLongRunningBase but I could check those things after and was able to make my code to compile.

The problem is that when I run my code I get this exception in the very begining and it just kills the service:

Method 'ExecuteMessage' in type 'ServiceStack.Host.ServiceController' from assembly 'ServiceStack, Version=4.0.9.0, Culture=neutral, PublicKeyToken=null' does not have an implementation.

I get this when hitting the base:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using ServiceStack;
using ServiceStack.Text;
//using ServiceStack.WebHost.Endpoints;
using ServiceStack.Web;


namespace ThisService {
    public class AppHost : AppHostHttpListenerPoolBase { //AppHostHttpListenerLongRunningBase {
        public AppHost(int wthreadMax)
            : base("This Service " + VcsInfo.ChangesetId, wthreadMax, typeof(ThisService).Assembly) {
        }
 ...

I am referencing in my project: ServiceStack (4.0.9.0); ServiceStack.Client; ServiceStack.Common; ServiceStack.Interfaces; ServiceStack.Text

I am sure I am doing something wrong changing to version 4.* and am lost with what is trying to call the Execute Message since I think removed everything from the previous version. Any suggestion to where I should be looking to?

By the way, this a simple service: get json -> math + stuff -> return json.

I want to find out if a bug I found the version 3.9.43 still happens in version 4.0.9 (can't find anything specific about that bug but I believe one fix there is related) to see if I should actually re-factor my code for this version.