When you see the error "Error: Path must be the form /foo" , the URL of your product page may have an unsupported character in it, such as a trademark or registered symbol.
Check that your product's path only contains letter, numbers, hyphens and underscores.
The product path field is located in the "edit website SEO" section at the bottom of the product dashboard in Shopify.
If that doesn't help, please email links to your store and the product page to firstname.lastname@example.org.
We'll take a look into the issue.