IChatAutomationClient addin is not valid

Content

I implemented IChatAutomationClient in an add in class no other add in are included but when loading the addin in addin manager it says there is no valid addin in the dll any idea on  how to implement IChatAutomationClient

Code Snippet

              [AddIn("ChatClient AddIn", Version = "1.0.0.0")]
    internal class ChatClient : IChatAutomationClient
    {
 public bool Initialize(IGlobalContext context)
        {
            _globalContext = context;
            _globalContext.LogMessage("ChatClient initialized");
            return true;
        }
 private IChatSession _chatSession;
 private IGlobalContext _globalContext;

public IChatSession ChatSession
        {
            get
            {
                return _chatSession;
            }
            set
            {
                _chatSession = value;
                _chatSession.SessionStatusEvent += _chatSession_SessionStatusEvent;
                _chatSession.SystemErrorEvent += _chatSession_SystemErrorEvent;
                _chatSession.EngagementAssignmentEvent += _chatSession_EngagementAssignmentEvent;
                _chatSession.EngagementRemovedEvent += _chatSession_EngagementRemovedEvent;
            }
        }
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}