Yes, I disabled all plugins except MailChimp for WooCommerce.
The opt-in checkbox is not visible anywhere on the checkout page.
FYI: the checkbox position setting has the entry: woocommerce_after_checkout_billing_form
The instructions for the checkbox position setting (accessible via link in the plugin) are not user-friendly at all. I cannot find any specifics on changing the position using this type of string.
A simple checkbox under the email entry field is all I need here.
Thank you