This error means Etsy refused to save a product because at least one of its variations reached Etsy without a price or a quantity.
Why it happens
You did not set anything up wrong. Shuttle always sends a quantity for every variation it builds from Shopify, using 1 when it cannot read a stock count. A price is sent only when Shopify returned one. The error appears only when the details were incomplete at the moment Shuttle ran:
Shopify sent a variation without a price. For a short time, Shopify gave Shuttle no price for a variation, so it reached Etsy without one.
The Etsy listing already had a variation without a quantity. When an update leaves a variation's quantity alone, whatever is on Etsy stays, and Etsy rejects the update if that variation had none. Check this in Etsy by opening the listing and looking at each variation's quantity.
A new attempt usually goes through, because Shuttle reads fresh product details each time.
How to fix it
Wait a few minutes, then open Shuttle and go to Products.
Choose the Shopify → Etsy tab and find the product.
If the product is already on Etsy, click Update in Etsy. On the All Products tab, click Update, then choose Update in Etsy.
If the product is not on Etsy yet, click Transfer to Etsy instead.
Confirm in the window that opens, then check that the product finishes without this error.
Still seeing it?
If the same product fails again after you retry, contact us through the chat bubble in Shuttle and tell us the product's name.