Client Context executeQuery() works in console app but returns null object when executed from CRM Server

I have the function GetDocumentLibrary which must return a libray from sharepoint site. When I execute it from a Visual Studio Console Application it works and return the library with all informations. But when I execute it from a CRM Plugin in CRM Server the query variable contains one result (that is right) but this result is null. Why it is null ? The two code are same.

          protected void ExecutePostContactCreate(LocalPluginContext localContext)
    {

        if (localContext == null)
        {
            throw new ArgumentNullException("localContext");
        }

        IPluginExecutionContext context = localContext.PluginExecutionContext;


        var candidatFirstName = "TestFN";
        var candidatLastName = "TestLN";
        string sharepointFolderName = candidatLastName + " " + candidatFirstName;

        //Site details
        string shpSite = "https://org.sharepoint.com/sites/website";
        string login = "login";
        string password = "password";
        string libName = "LibName";

        var securePassword = new SecureString();
        foreach (char c in password) securePassword.AppendChar(c);

        var onlineCredentials = new SharePointOnlineCredentials(login, securePassword);


        using (ClientContext clientContext = new ClientContext(shpSite))
        {
            clientContext.Credentials = onlineCredentials;
            Web web = clientContext.Web;
            clientContext.Load(web);

            clientContext.ExecuteQuery();

            //Créate sharepoint folder
            CreateFolder(clientContext, web, libName, sharepointFolderName);

        }
    }


    private void CreateFolder(ClientContext clientContext, Web web, string libraryName, string folder)
    {
        try
        {
            var list = GetDocumentLibrary(clientContext, web, libraryName);
            if (list != null)
            {
                var folders = list.RootFolder.Folders;
                clientContext.Load(folders);
                clientContext.ExecuteQuery();
                var newFolder = folders.Add(folder);
                clientContext.ExecuteQuery();
            }
            else
                throw new Exception("Test");
        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);
        }
    }

    private List GetDocumentLibrary(ClientContext clientContext, Web web, string libraryName)
    {
        try
        {
            if (web != null)
            {
                var query = clientContext.LoadQuery(
                web.Lists.Where(p => p.Title == libraryName));
                clientContext.ExecuteQuery();
                return query.FirstOrDefault(); //Returns Null when exectude from CRM plugin but works from VS Console App;
            }
        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);
        }
        return null;
    }