Cannot reach the second level cache using .NET NHibernate on Windows

I try to use Couchbase as a second level cache in a .NET 4.0 console (batch) application using NHibernate on Windows.

I installed Couchbase-server 2.1.1 on server and the last provider (NHibernate.Caches.Couchbase via Nuget) in my console application.

According to NHibernate profiler, the provider seems to work perfectly (the provider send the command to cache the classes configured to be cached) but I am facing an issue : the cache is unreacheable.

When a cache order is sent, the following message is displayed in NHibernate profiler:
could not save: ORMClassName#Id => Item{version=,freshTimestamp=NNNN}

Am I missing some credentials to grant from the server ?
I followed the installation tutorial on Couchbase site :
I opened port 8091 (which is the default bucket port I want to access) and I get access to the REST web console via navigator on my development machine but I cannot access the store.

here is an extract of my config :

where XXX is the hostname I put on Server Node name while installing Couchbase Server.
I tried too.

Thank you if you have an answer.
Best Regards,