Hi,
Can you check if your Acymailing is still being triggered by the cron job? You can see the last run time in Configuration->Queue process.
If your cron is functioning properly please inform us about the exact version you're using. You'll find it in the top right corner of your Acymailing.
And please check the action targets tab of your automation. It will show you the number of users that match your conditions. If it's zero nothing will be send.