I've got a 3B+ who's only job is running pi-hole for my home network. It is behind a UPS. Plus I have a cute little Adafruit OLED display on it that shows four lines of text (IP address, how many clients connected, how many ads blocked, etc.) This morning I suddenly started having web access problems on a different computer and traced the issue to pi-hole not responding. I couldn't even SSH in so I pulled the power cord, waited a minute and plugged it back in. However, no activity light blinking and it never booted. I tried again, plus tried other SD cards, plus removed the OLED display, plus tried a different power supply...nothing.
1.) how can a Pi just die like that? It is surge suppressed and everything?!
2.) how can I test if the SD card is bad? I heard they go bad after a while, or something like that. It's only been about a year or so but it has been running pretty much 24/7.
3.) what is an easy way to tell if the hardware is dead? Are there tests I can do on it? Since I can't boot it even from several different SD cards, perhaps testing the voltage in different places would tell me something, if so, where?
Now I guess I should have made a mirror copy of that SD card since I had special drivers for the OLED and had modified pi-hole to use DNS over HTTPS for privacy. Lesson learned.