Simon 5 is coming soon!
Simon version 5 is currently in beta testing. It is a massive update, introducing a much-requested feature: syncing the Simon data between multiple Macs, plus a Simon Status service, a Link Checker filter, improved Find filter, iMessage and Speak Error notifiers, a new app icon, and much more.
Important: please note that Simon 5 requires a minimum of macOS 10.12 (Sierra), and will be a paid upgrade from Simon 4 after the beta. Purchasers since September 1, 2020 automatically get a version 5 license (that also works in previous versions).
Re: can i change the "failed" "recovered" subject line
There isn't any easy way to change the terms used in Simon, but you can certainly customize the email. You can edit the email notifier to use whatever text you wish. Simply replace the status variable with the text you prefer, and use separate notifiers for changes, failures and recoveries.