Problem with couchbase

Odd.cs

using System;
using System.Linq;
using CouchBasePerf.Domain;
using Enyim.Caching.Memcached;

namespace CouchBasePerf.Handlers
{
    public class HandlerBase
    {
        protected Couchbase.CouchbaseClient client = new Couchbase.CouchbaseClient();

        protected void HandleConcurrent<T>(string Id, Action<T> Change) where T : AR, new()
        {
            CasResult<bool> casResult = new CasResult<bool>();
            do
            {
                var cas = client.GetWithCas<T>(Id);
                var instance = cas.Result ?? new T { Id = Id };
                Change(instance);

                if (instance.Changes.Any())
                {
                    if (cas.Result == null)
                        // this keeps returning false ?
                        casResult.Result = client.Store(StoreMode.Add, Id, instance);
                    else
                        casResult = client.Cas(StoreMode.Set, Id, instance, cas.Cas);
                }
                else
                {
                    casResult.Result = true;
                }
            } while (casResult.Result == false);
        }

        public void Execute<T>(T cmd)
        {
            (this as dynamic).Handle(cmd);
        }
    }
}

StoreMode.Add keeps returning false forever... what's wrong here ?