Version 1.9.1 of the WooCommerce Zapier plugin has just been released.
This release implements a hotfix for users that have upgraded to WooCommerce Zapier version 1.9.0 and have a web hosting environment that has PHP opcode caching enabled with opcache.save_comments=0.
Update today!
The latest plugin version can be downloaded via your WordPress dashboard, or via the WooCommerce.com my account page.