I’m having this issue with a site as well. What version are you on? I’m on Version 4.1.14 of the plugin and WooCommerce Version 3.5.5.
We’re on WordPress 5.1. Could it be a conflict with that?
The first three errors are pretty easy to fix. Just add “public static” to the beginning of each function definition.
Any ideas on the last three errors or an ETA on a fix? I’ve seen this after an upgrade to WP 4.4.0