"Unable to reserve inventory" when placing a Shopify order

Overview

You place an order for a creator against your Shopify store and it fails with Unable to reserve inventory, even though the products show stock in GRIN.

Two things explain the mismatch.

First, that message is not GRIN's own stock check. It is what Shopify answered when GRIN tried to create the order, and GRIN shows the store's wording as it comes.

Second, the quantities you see in GRIN come from the last sync of your catalog. That is not the number Shopify checks at the moment the order goes out, so GRIN can show stock while Shopify refuses.

Why Shopify gets to refuse

There is a setting on your Shopify store connection called Stop orders from being created when products are out of stock?. Its description reads: enable this option to prevent a creator fulfillment order from being created if one of the products in that order is out of stock.

When it is on, GRIN tells Shopify to obey its own inventory policy, so Shopify itself declines the order when a line item cannot be reserved. When it is off, GRIN tells Shopify to ignore that policy, and the order is created even when a product is out of stock.

What to check first

1. Open the failed order and note every product on it.
2. In Shopify, look at the available quantity for each of those variants right now, not the quantity in GRIN.
3. Check whether any of them sit at zero available while still showing stock on hand. Committed or reserved units are the usual reason for that gap.
4. Also check your product minimum threshold. If a variant's inventory is at or below the threshold you set, GRIN treats it as out of stock even when Shopify still shows quantity available. This and the rest of the sync behaviour are covered in the Shopify product sync troubleshooting guide.

How to change the setting

The setting is per store connection, so it belongs to one Brand and does not affect your other stores.

1. Go to Brands and open the brand connected to the store.
2. In the Manage list, open Connection Settings.
3. Find Stop orders from being created when products are out of stock? and switch it off if you want orders to be created regardless of what the store reports.

Turning it off is a real trade-off, not just a workaround. It removes the guard that stopped this order, so you can end up creating orders your store cannot fulfil. Leave it on if you would rather catch stock problems at order time.

Related

For the order steps in an Activation, see fulfilling orders in an Activation. For the rest of the store connection options, see Shopify connection settings.