We may be getting closer to root cause.
As a test I configured Email Notification to send the sensor stats as an email message once every hour. I did this Sunday at 12:00 noon and started receiving hourly emails until this morning when the Davey Jones skimmate locker sensor tripped the alarm. When that happened, the P4 shut down the skimmer as it is supposed to. When I emptied the skimmate locker, the GCC software automatically reset itself as configured to and the skimmer started functioning again. The alarm message no longer appeared in either the GCC app or the P4 display. All good right? Well, the hourly notifications stopped and that's not good.
I rebooted the P4 this evening to see if the emails would start sending again and sure enough they are sending once again.
Any thoughts on why the P4 has to be rebooted to start sending email notifications?