Things that can go wrong when installing good old #smokeping:

You're using fping as a probe, but in debug mode, smokeping shows it returns "can't create socket" (at least when you're not running smokeping --debug as root 🙄)...

In my case it seems that /usr/bin/fping has lost their capability attributes at some time in the past, so it only worked when started by root. I reinstalled the fping package, and now things are back to normal...

# getcap /usr/bin/fping
/usr/bin/fping = cap_net_raw+ep