When creating a configurable product with child products which are ‘automatically’ generated. These child items will have no weight. As a result, they are virtual products and virtual products don’t have a shipping method because we don’t need to ship the virtual product in Magento. there are no delivery methods in virtual products.
By changing type_id in the catalog_product_entity table you can resolve this issue.
You can convert all virtual products to the simple product by just one query.
update catalog_product_entity set type_id = 'simple' where type_id = 'virtual';
But beware, this query converts all virtual products to simple. (better to create DB backup before the start)