No emails for approval | Approval notification not working

We recently started using the Pending Submission Notification plugin for our website, https://www.indianmomsconnect.com. It worked fine and we were receiving both pending review and approval emails. But from this Tuesday, we started noticing that when the submission is approved by an admin, an email notification is not getting sent.

We checked our email configuration settings and it all looks ok. Not sure what went wrong.
Any help/guidance on this would be much appreciated.

Thanks in Advance.