The following can be a reason why inventory is showing 0 stock:

Although inventory rules are in most cases assigned to stores in general, they can be overridden on the Listings page on specific listings. Therefore, when a product shows out of stock, you can search for this product on the listings page and see what Inventory rule is assigned to it. The inventory rule might be the answer for the amount of inventory you see on your marketplace.

Some things to look for when reviewing your inventory rule:

• See if the rule is assigned to the store this product is listed on.

• Identify if the rule has a max quantity.

• Check if the rule has set up a “Favorite store setting”.

• Determine if the “restock date” on the rule is set to the correct date. (if there is one set)

• Take a look if the “Manual Inventory” is turned on.

These are all factors that can make a difference in the inventory of products. See below 2 articles explaining in detail how these factors affect the number of inventory reported to the marketplaces.

https://faq.inventoryahead.com/how-to-set-up-inventory-rules-2/

https://faq.inventoryahead.com/how-to-set-up-your-vacation-settings/