MailPoet WP eCommerce Add-On Manual Placement

Hi There,

I’m trying to create a shortcode to manually paste the checkbox. On my current form, the newsletter checkbox closes when they check the ‘Same As Billing’ box.

On line 203 of mailpoet-wp-ecommerce-addon.php, I’ve got:

add_shortcode('newsletter', array($this, 'newsletter_shortcode'));
        }

        public function newsletter_shortcode() {
                return 'Hello Word!';
        }

But it’s not working. I’m not the best at php, so any help would be appreciated! Maybe there is a better solution as well?

Thanks

https://www.ads-software.com/plugins/wysija-newsletters/