Hi @rayeason,
Hope you are doing well.
Sorry to hear that still your issue is not fixed.
If you are using the Sales notification type. Then please remove the corresponding sales order (which are your test orders) from here: WP Admin Dashboard > WooCommerce > Orders
After removing the orders, please regenerate your sales notification from NotificationX > All NotificationX and then regenerate by clicking the regenerate button. Check this screenshot.
Hope this will help you. If you are still getting the notification on your site, please let me know which type of Notification you are testing. So we can check and help you accordingly. And you can share the website URL as well.
Let us know the update. Thanks!