Return xml with 406, Net Core 2.2, with Formatfilter?

Question

I’m trying to make a comeback in mine Controller with FormatFilter .xml, but I get the 406.

Controller:

[HttpGet("xml/loja/{id}/{format}"), FormatFilter]
[Produces("application/xml")]
[AllowAnonymous]
public async Task<ActionResult<filterResultSet>> GetXmlLoja(
    [FromHeader] Guid userId, 
    [FromHeader] string fileName, 
    Guid id
) 
{ 
    //FormatFilterAttribute format = FormatFilterAttribute.GetCustomAttribute(XmlDocument)
    //if (!_mapaRelatorioBO.Exists(id).Result) return NotFound(new { message = "MapaRelatorio não existente!" });
    //if (userId == null) return BadRequest(new { message = "Usuário não informado!" });
    return await _mapaRelatorioBO.GetXmlLoja(id, fileName);
}

Startup.Cs

services.AddMvcCore(options =>
{
    options.FormatterMappings.SetMediaTypeMappingForFormat
        ("xml", MediaTypeHeaderValue.Parse("application/xml"));
    options.FormatterMappings.SetMediaTypeMappingForFormat
        ("config", MediaTypeHeaderValue.Parse("application/xml"));
    options.FormatterMappings.SetMediaTypeMappingForFormat
        ("js", MediaTypeHeaderValue.Parse("application/json"));
})
.AddFormatterMappings();

services.AddMvc(options =>
{
    options.OutputFormatters.Add(new XmlSerializerOutputFormatter());
});

Return

The format of the submission is: filterResultSet filter = new filterResultSet();

namespace GI.NET.Insights.Dominio.Xml
{
    public class EstruturaLojaXml
    {


    }


    // NOTE: Generated code may require at least .NET Framework 4.5 or .NET Core/Standard 2.0.
    /// <remarks/>
    [System.SerializableAttribute()]
    [System.ComponentModel.DesignerCategoryAttribute("code")]
    [System.Xml.Serialization.XmlTypeAttribute(AnonymousType = true, Namespace = "http")]
    [System.Xml.Serialization.XmlRootAttribute(Namespace = "http", IsNullable = false)]
    public partial class filterResultSet
    {

        private filterResultSetFilterResult filterResultField;

        /// <remarks/>
        public filterResultSetFilterResult filterResult
        {
            get
            {
                return this.filterResultField;
            }
            set
            {
                this.filterResultField = value;
            }
        }
    } ...

by the result that should be successful the Swagger shows me so: