Shuttle did not send a Shopify stock change to this Etsy listing. Etsy tracks the listing's stock on one of its options, and your settings tell Shuttle to skip listings like this.
Why it happens
Etsy tracks stock on one option. The listing has two options, for example Size and Colour, but its quantity varies for only one of them. Etsy then keeps one stock number for each value of that option. For example, there is one quantity for each Size, and every Colour shares it.
Your setting is off. In your Stock Syncer settings, "Update Etsy variations based on the option that manages stock" is turned off. While it is off, Shuttle skips the stock update for these listings when stock syncs from Shopify to Etsy.
How to fix it
To let Shuttle update these listings:
Open Stock Syncer and click Settings.
Open the Shopify → Etsy page.
Under Quantity managed on an Etsy option, tick Update Etsy variations based on the option that manages stock.
Click Save.
After this, a stock change in Shopify updates every Etsy variation that shares that option value. For example, if Etsy tracks stock on Size, a Shopify sale of Size Small updates every Etsy variation where Size is Small.
To keep a separate quantity for each variation on Etsy instead:
Open the listing on Etsy.
Choose Edit quantity options next to Quantity.
Tick every option so quantities vary for each variation, then save.
Check the quantities on Etsy. The shared stock is now split into a separate number for each variation.
For more on how Etsy tracks stock, see Handling Etsy Stock Management by Product or Option Level.
Still seeing it?
If the setting is on and new stock syncs for this product still show this message, contact our support team. Tell us the product name.