notification not sending posts

This plugin was working perfectly and then for no apparent reason the emails on any new posts to the blog stopped working. I have done the troubleshooting recommended but no answers. If I send a manual email to myself it works. Is there a way to fix this or should I move onto another plugin. I hate to do that as this one has been successful previously. Is there a fix?

https://ww.wp.xz.cn/plugins/email-subscribers/