Migration of Product Variants to WooCommerce has some limitations due to platform’s architecture. If during WooCommerce import the number of combinations for Variable Product exaggerates 1000, LitExtension will migrate this product as simple and skip all related options.
As an alternative, you can move your product options to WooCommerce Add-Ons plugin. To set up migration to this plugin you need only to install it and then activate it in WooCommerce.
BUT during the migration to Add-Ons plugin, products will not have variants in your admin section, ONLY options.