Hello pnuiten,
Thanks for reaching out to us!
I’m sorry you’re having troubles getting our plugins working. Hopefully we can get this issue resolved for you quickly.
Our WooTickets plugin works in conjunction with the WooCommerce plugin. Based on the warning you’ve provided, it looks like you don’t have WooCommerce installed and activated. You’ll first need to download and activate WooCommerce from the WordPress.org repository before you can use our WooTickets plugin.
Let me know if you continue to have issues activating after installing WooCommerce.
Thanks!