To solve just open phpMyAdmin
and run this query.
NOTE: You need to replace table prefix ac_ with yours and check what ID of your second store. As you see below i set "1 as store_id". If your second store have another - your should to replace with yours too.
SET SQL_MODE='';
INSERT INTO `ac_email_templates`
(`status`, `text_id`, `language_id`, `headers`, `subject`, `html_body`, `text_body`, `allowed_placeholders`, `date_deleted`, `store_id`)
SELECT `status`, `text_id`, `language_id`, `headers`, `subject`, `html_body`, `text_body`, `allowed_placeholders`, `date_deleted`, 1 as `store_id`
FROM `ac_email_templates`
WHERE `store_id` = 0;