WooCommerce 3.0 is a major update, it was released on 04, April. Please don’t upgrade WC on your site at this moment. Our developer team is working on new theme update and it will be released soon. If you have already updated WC plugin, please downgrade to the previous version. You can download the previous version here https://downloads.wordpress.org/plugin/woocommerce.2.6.14.zip
The version 2.6.14 is a stable one, which is fully compatible with the current theme version.
There are different problems with products displaying and processing may occur if you use the latest woocommerce.