Error while generating the sitemap

Error
MultiLanguage Sitemap

System.InvalidOperationException: Operation is not valid due to the current state of the object.
   at FoxNetSoft.Plugin.Misc.MultiLanguageSitemap.Factories.SitemapMultiLanguageModelFactory.PrepareSitemapXmlModelAsync(Int32 id)
   at FoxNetSoft.Plugin.Misc.MultiLanguageSitemap.Controllers.MultiLanguageSitemapController.SitemapXml(Nullable`1 id)

What nopcommerce version do you use?

4.60.6