How Inventory Levels Syncing Works

First, you need to correctly configure WooCommerce to handle stock / inventory.

Then, make sure you have enabled the WooCommerce Amazon Fulfillment plugin settings for syncing stock levels under WooCommerce > Amazon Fulfillment.

Once those are both set up, WooCommerce Amazon Fulfillment will automatically pull inventory numbers from FBA depending on whether you’ve enabled one or both sync modes:

1. The first one pulls the latest stock level per product included in an order after the order is placed in WooCommerce. This helps keep individual items updated as they sell in your store with the latest numbers from Amazon.
2. The second method checks Amazon hourly and retrieves the latest numbers for all products that have had inventory level changes within the previous 24 hours.

Both methods can be active at the same time for the best inventory syncing coverage possible. If you have the second option turned on (to sync every hour) it will also create a log of the sync events and the numbers that were updated in a file called:
yourdomain.com/wp-content/plugins/ns-fba-for-woocommerce/logs/ns-fba-inventory-log.html
You can open that and see all the sync’s that have happened.

The Sync Inventory Now button is useful after lots of new products are loaded into WooCommerce or for brand new sites syncing for the first time and other similar scenarios. This will pull numbers for all products that have had inventory level changes in Amazon over the previous year and update those numbers in WooCommerce. For large stores this might take a while to complete.