In other to provide you with a better support experience, please make sure that:
You have updated the plugin to the latest version, learn how to do that here.
Try deactivating all plugins but leave only YayMail and WooCommerce - if the issue is solved then it means the problem is from an external plugin, then you can activate them one by one to detect the exact one causing the issue and check it with their support.
You have checked them all but still cannot find a solution? Contact Us