Hi @tekniq!
I visited your site to make a purchase test and confirmed the message on the checkout page.
Usually, this kind of issue could be related to a conflict between WooCommerce and your theme or another plugin; an outdated or malfunctioning code could be interfering.
To be sure of this, please perform a conflict test by temporarily switching your theme back to Storefront, disabling all plugins except WooCommerce, and then check again if the issue persists.
If that solves it, reactivate the theme first and check again. Then, reactivate your other plugins, testing after each, until you find the one causing conflict.
If you cannot perform a conflict test on your live site, we recommend creating a staging site using the WP Staging plugin.
You can find a more detailed explanation of how to do a conflict test here: https://docs.woocommerce.com/document/how-to-test-for-conflicts/.
Let us know how that goes for you!
