@RDinformarica I’ve addressed the device-going-offline problem two ways.
Agreed with @PeteKnight, and have moved entirely to the WiFi-enabled ESP32 and ESP8266 devices.
Way One. In the code of the monitored ESP device, I periodically check to see if it’s connected to WiFi. If not, and after an appropriate waiting period, I reboot the device from its own code. This is good as long as the device, itself, remains powered. The device reboots, tries to connect to WiFi, and reboots again after a time if it cannot connect. The only drawback here is that you never know the device is offline. Only the device knows. I have not attempted to use the Blynk notification to do anything when a device goes offline.
Way Two. I have the device I’m monitoring do routine ‘check-ins’ with my watchdog device. I use periodic HTTP ‘update’ calls from the devices being monitored to a Blynk datastream on the watchdog device. When the watchdog’s Blynk datastream gets hit, BLYNK_WRITE gets called and I reset the clock. The watchdog periodically checks to see how long since the last ‘check-in’ from each monitored device and takes action with too much time is elapsed. Usually, it’s as simple as sending me a notification or coloring a Blynk widget red.
On one of my systems, however, I have a WiFi switch (SONOFF or Shelly) powering the monitored device. On a fatal error, the watchdog turns the device’s power switch off, then on again after 60 seconds for a ‘cold’ reboot of the monitored device.
If helpful, I will publish my code for doing an HTTP ‘update’ to a remote Blynk device’s datastream. I use this code for communicating among Blynk devices all the time.
Hope this is helpful. .