-Server down HA unavailable
-network down HA unavailable
-HA down (application issue)
I think all case require external (different server/network) service to check for HA and report if down and every scenario I previously imagine it not seem worth time and thought it best to Prevent Failure in first place since that is actual desire.
Maybe send "hello’ to IFTT every [xx]minutes.
If message not receive [x2] send notification to …
Not sure if that possible but that or similar would work.
You can do opposite where HA must cancel some message or it gets sent. Like plot from movie where the guy meets up to pick up kidnap person but make sure they must keep him alive else everything on SD card is sent to news outlets…
Now I find out by some automation not working, or opening the app, and can’t connect (Host wor ks), so I manually restart (sometimes works, sometimes I have to reboot, sometimes reboot twice).