Ensure each of your Products in Shopify are enabled to require shipping and Shopify tracks the products inventory.

To enable Orders sync:
At your Shopify admin Products section, in the Product details select the option near the bottom page for This product requires shipping.
* If you have Variant products, then each Variant will need to have this option selected.Shopify will not send a Product to Appath if it is not setup to require shipping and set as manual for Fulfillment.

To enable Inventory sync:
In your Shopify admin Products section, in the Product details select the option under Inventory policy to Shopify tracks this product’s inventory.

Shopify Product info can be found on their site at:
https://help.shopify.com/manual/products/add-update-products

Shopify support can be reached at:
https://support.shopify.com