WebService Session variable null when trying to read in another method call

Question

I have the problem as stated that my Session object is null when called in another method after it is set in the first method.

i have one abstract class that i inherit from that looks like this

public abstract class ProxyApiService : WebService, IRequiresSessionState
{
    [WebMethod(EnableSession = true)]
    protected virtual string GetSecret()
    {
        throw new NotImplementedException("You forgot to override in derived class");
    }
}

And the class that tries to read the session like this

public class APIKey : ProxyApiService 
{
    [WebMethod(EnableSession = true)]
    protected override string GetSecret()
    {
       return HttpContext.Current.Session["GUID"].ToString();
    }

    [WebMethod(EnableSession = true)]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public string setAPIKey(string path)
    {
        // Get data...
        var guidStr = "Test";
        HttpContext.Current.Session["GUID"] = guidStr;

        return "";
    }

    [WebMethod(EnableSession = true)]
    protected override string GetSecret()
    {
       return HttpContext.Current.Session["GUID"].ToString();
    }
}