If you are having trouble updating stock to your WooCommerce integration and are seeing the error message "Invalid API response, unexpected character violation.....", the issue is typically caused one of the reasons:
Your WooCommerce site is down and you can confirm to see if it properly loads on a separate browser tab.
The most common reason is your firewall software is blocking Finale network connections to your WooCommerce installation. The link below states how to rectify this situation.