I’m having the same problem. In the Diagnostic panel the under the Semaphores tab it says:
( WordPress Cron System ENABLED. (it’s ok) )
But under the delivery engine it says this:
( Delivery Engine It seems the cron system is not working. Reload the page to see if this message change.
If inactive or always in “running now” status your blog has a problem: read more here. )
I’m not sure what to do next.
The site the newsletter plugin is installed on is my in house kiosk running on a n iPad that doesn’t get used but maybe a few times a day right now. The kiosk program does refresh and reload the home page every 2 minutes.
In the Diagnostic Panel under the Semaphores and Cron’s Tab when I click the Trigger Button the delivery engine counts down till the next scheduled email.
It looks like it is working.
I have Godaddy for my email so I have the newsletter sending only 100 emails a day.
All test emails work. Sorry, I’m a newb to all this.