If you are getting this error it means your existing shipping or assigned shipping in the profile is somehow removed or moved away. To resolve this, you need to follow some steps:
1.) Fetch the shipping template from the Etsy. Go to the Templates section of the App.
2.) Click on the "Fetch shipping" option.
3.) Assign the shipping template in the profile to which your product belongs by editing the profile.
4.) Republish the products from the "All products" section of the App.