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

System.ArgumentException: The given field name does not exist in the given index schema. Field: 'VariantGroup_VARGRP1', Index: 'Products.index'.
   at Dynamicweb.Indexing.Lucene.Helpers.ParseQueryExpressionInternal(IIndex index, Expression expression, Analyzer analyzer, QuerySettings settings)
   at Dynamicweb.Indexing.Lucene.Helpers.ParseQueryExpressionInternal(IIndex index, Expression expression, Analyzer analyzer, QuerySettings settings)
   at Dynamicweb.Indexing.Lucene.Helpers.ParseQueryExpressionInternal(IIndex index, Expression expression, Analyzer analyzer, QuerySettings settings)
   at Dynamicweb.Indexing.Lucene.Helpers.ParseQueryExpression(IIndex index, Expression expression, QuerySettings settings)
   at Dynamicweb.Indexing.Lucene.LuceneIndexProvider.SearchInternal(IQuery query, QuerySettings settings)
   at Dynamicweb.Indexing.Lucene.LuceneIndexProvider.Query(IQuery query, QuerySettings settings)
   at Dynamicweb.Indexing.Queries.IndexQueryProvider.Query(IQuery query, QuerySettings settings)
   at Dynamicweb.Indexing.Querying.QueryService.Query(IQuery query, QuerySettings settings)
   at Dynamicweb.Ecommerce.Indexing.ProductQueryHelper.ExecuteQuery(IQuery query, QuerySettings settings)
   at Dynamicweb.Ecommerce.Indexing.ProductQueryHelper.GetProductsAutoIdsFromIndexQuery(IQuery query, ProductCatalogSettings settings, QuerySettings querySettings, IEnumerable`1& facetViewModel, IEnumerable`1& spellCheckerResult)
   at Dynamicweb.Ecommerce.ProductCatalog.ProductCatalogFrontend.RenderProductList(ProductCatalogSettings settings, QuerySettings querySettings, IQuery query, String groupId, Boolean feed)
   at Dynamicweb.Ecommerce.ProductCatalog.ProductCatalogFrontend.GetContent()
   at Dynamicweb.Frontend.Content.GetModuleOutput(Paragraph paragraph, PageView pageview)