Only some blog notifications being sent, not all

Hi,
We have notifications configured for new blog posts...these notifications are going to some subscribers, but not all. The cron job is set up and working. I went to this URL:
index.php?option=com_easyblog&view=spools

And I see that there are 60 pending notifications that have not yet been sent, all of which were created on 8/14/15. The cron job runs every hour, so they definitely should have all been sent by now. In the "Email Processing" settings, "Process how many emails at a time" is set to 100.

I tried running the cron job command manually:
/usr/bin/wget -O /dev/null "http://causeeffective.org/index.php?option=com_easyblog&task=cron";

But the emails in the spool were still not sent.

Any ideas?

Thanks,
Matt