An error occured while attaching module (Dynamicweb.Frontend.Content)

System.NullReferenceException: Object reference not set to an instance of an object.
   at Dynamicweb.eCommerce.Products.Group.get_AllGroupsByLanguageID(String languageID)
   at Dynamicweb.eCommerce.Products.Group.GetGroupByID(String groupID, String languageID)
   at Dynamicweb.eCommerce.Products.Group.GetGroupCategoryFieldValue(String groupId, String languageId, Field field)
   at Dynamicweb.eCommerce.Products.Group._Closure$__295._Lambda$__1181(String groupId, String langId, Field f, Boolean isInheritedVal)
   at Dynamicweb.eCommerce.Products.Group._Closure$__295._Lambda$__1182(String groupId, String languageId, Field f, Boolean isInheritedVal)
   at Dynamicweb.eCommerce.Products.Group.GetCategoryFieldValue(String grpId, String grpLangId, Func`4 getGroupFieldVal, Field field, Nullable`1 currentValOnlyOrInheritedValOnly, String defaultLanguageId)
   at Dynamicweb.eCommerce.Products.Product.GetDefaultCategoryValue(String productId, String variantId, String languageId, String defaultLanguageId, IEnumerable`1 groupsIds, String primaryGroupId, Func`5 getProdFieldVal, Func`4 getGroupFieldVal, Field catField)
   at Dynamicweb.eCommerce.Products.Product.GetCategoryValue(String categoryID, String fieldID, Boolean includeInheritance)
   at Dynamicweb.eCommerce.Frontend.Renderer.GetProductCategoryFieldValue(Product product, String categoryID, Field field)
   at Dynamicweb.eCommerce.Frontend.Renderer.RenderProductCategoryFields(Product product, Category category, Template template, String loopName)
   at Dynamicweb.eCommerce.Frontend.Renderer.RenderProductCategories(Product product, Template template, String loopName)
   at Dynamicweb.eCommerce.Frontend.Renderer.RenderProduct(Product Product, Boolean ExtendedProperties, Template Template, Int32 loopCounter, Boolean renderRelated, String productURL, Int32 quantity, Int32 wishListID, Boolean renderPublicList, Int32 orderLineOfProductCount)
   at Dynamicweb.eCommerce.Frontend.Renderer.RenderProduct(Product Product, Boolean ExtendedProperties)
   at Dynamicweb.eCommerce.Frontend.Frontend.EcomRender()
   at Dynamicweb.eCommerce.Frontend.Frontend.GetContent()
   at Dynamicweb.Frontend.Content.GetModule(DataRow& ParagraphRow)