Emails nor being sent to all users

Hi,

I’m using your plugin for a long time and from last couple of days the emails are not being sent to all the users.

I have also followed your article here : https://www.icegram.com/documentation/es-new-post-notification-emails-are-not-being-received-by-subscribers/

But still not able to solve the problem.

I’m attaching a screenshot here: https://prntscr.com/kmc6bx
When the end date shows 0000 , those are the mails which are not sent to all the subscribers.

Looking for your quick help.

Regards,