Due to the peculiarities of Shopify operation, it sets restrictions for product variants. So, It's not allowed to migrate each product with more than 99 variants and 3 characteristics from PrestaShop to Shopify. Verify the application helps you to map facts from your PrestaShop store to the suitable fields in https://addons.prestashop.com/es/seo-posicionamiento-buscadores/31857-google-rich-snippets-automatico-json-ld-opengraph-seo.html