<OtherMovableObject xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns:z="http://schemas.microsoft.com/2003/10/Serialization/" xmlns="http://schemas.datacontract.org/2004/07/Rgi.Data.Rightholder" z:Id="1">

XmlDocument doc = new XmlDocument();
            doc.Load(@"c:\Users\bobrovPV\Downloads\CardData3.xml");

            XmlNamespaceManager ns = new XmlNamespaceManager(doc.NameTable);
            ns.AddNamespace("i", "http://www.w3.org/2001/XMLSchema-instance");
            ns.AddNamespace("z", "http://schemas.microsoft.com/2003/10/Serialization/");
            ns.AddNamespace("", "http://schemas.datacontract.org/2004/07/Rgi.Data.Rightholder");

            var nodes = doc.SelectNodes("/OtherMovableObject", ns);
            foreach (var item in nodes)
            {
                
            }

XmlDocument doc = new XmlDocument();
            doc.Load(@"c:\Users\bobrovPV\Downloads\CardData3.xml");

            XmlNamespaceManager ns = new XmlNamespaceManager(doc.NameTable);
            ns.AddNamespace("i", "http://www.w3.org/2001/XMLSchema-instance");
            ns.AddNamespace("z", "http://schemas.microsoft.com/2003/10/Serialization/");
            ns.AddNamespace("ab", "http://schemas.datacontract.org/2004/07/Rgi.Data.Rightholder");

            var nodes = doc.SelectNodes("/ab:OtherMovableObject", ns);
            foreach (var item in nodes)
            {
                
            }