There are a few aspects of WooCommerce's inventory that are not actively supported by Thrive.
Below are the most common restrictions:
Products marked as "downloadable"
Thrive does NOT track downloadable products. You can still track them in WooCommerce, but they will not appear in Thrive.
Selectable variations (a.k.a. "variants")
Products with selectable variations in WooCommerce must be assigned to a single attribute term in WooCommerce.
Products that are not simple or variable types in WooCommerce
Change the product type in WooCommerce and import again from the Locations & Integrations tab in Thrive.
Products that are set up as variable-type products but do not have any variations assigned to them in WooCommerce
Add at least one variation to the products in WooCommerce and import again from the Locations & Integrations tab in Thrive.