This error means Etsy found no domestic service in the product's shipping profile that accepts the weight Shuttle sent.
Why it happens
The weight is over every domestic limit. Each domestic service in an Etsy shipping profile has its own weight limit, so a profile that works for lighter products can still fail here. Shuttle sends the weight of the product's first variant in Shopify.
The product has no weight in Shopify. Shuttle then uses the Weight metafield if you named one, otherwise your Default weight. On a calculated shipping profile with neither, Shuttle sends 5 in your weight unit, which can be over the limit.
The weight unit is wrong. Default weight and metafield values are read in the Weight unit you chose.
The product gets a different profile than you expect. Products follow your shipping profile matches, or your collection mapping if your Shopify store uses market-driven shipping. Unmatched products get your Etsy default profile.
How to fix it
In Shopify, check the weight of the product's first variant. Correct it if it is wrong.
If the product has no weight in Shopify, open Settings → Products → General → Shopify metafields. If a Weight metafield is named, fill it in on the product. If not, set Default weight under Settings → Products → Shopify → Etsy → Dimensions & Weight.
On the Dimensions & Weight card, check that Weight unit matches the numbers you entered.
Go to Settings → Catalog Mapping → Shipping Profiles and check the Etsy default and Match shipping profiles. If that page says your Shopify store moved to market-driven shipping, check Settings → Catalog Mapping → Shipping → Collections instead.
In Etsy, open that shipping profile. Raise a domestic service's weight limit, or add a service that covers the weight.
Transfer the product again.
Still seeing it?
If the weight is correct and a domestic service covers it, contact support. Tell us the product name and the shipping profile it should use.