Cron Job for e-Newsletter No Longer Working

I have been sending e-newsletters via your plugin to my website members for years, at a regular interval of about every 3 months. Last week, I went to send my most recent letter using Cron per usual, and the Reports show it will send to about 2-3 members, including me, but it will not send to any of the other 300+ members of my website, and the Cron Job stays on hold.

I have not added to or altered my website or plugins from the last time e-Newsletter worked, and other emails from the website, including daily security emails to me and new member registration emails to new members, are going out from the site and working correctly.

I have granted access to my website via the WPMU DEV plugin for support staff to view the e-Newsletter Reports and current configurations. Please assist me with correcting this error with your plugin so that I may get my newsletters out to website members. Thank you.