Hello,
I discovered that the Brevo woocommerce plugin was putting a « REQUIRED » newsletter opt in checkbox on my checkout page. Every order required the customer to opt in to my newsletter, otherwise they could not place the order.
I found in the Plugin code src > mangers > cart-events-manager.php line 564 'required' => true, should be 'required' => false,
With this change customers now have the « Option » to sign up for my newsletter or not while checking out online. It is nolonger a requirement for the order to be placed.