Hi,
It could be that you did configure Acymaling for manual send only, or your cron is not being triggered or you have zero action targets in your automatic newsletter.
If your automatic send process is workjing, then your cron is ok. If you're not sure, go to Configuration->Queue process and check when the cron triggered your site. On top of the same page you can check if your rpocess is configured for automatic sending.
If the above is ok go to the Action targets tab of your automatic campaign. It should display how many users are targeted. If it's zero nothing will be send.