If If your CSN is unable to show the CAStor nodes via the Web console, then avahi-daemon is most likely not running.
Please Please check with "service avahi-daemon status", if the daemon is not running there can be 2 reasons:
1 - the The messagebus service is not running , .
Resolution: type "service messagebus start"
2 - you You ran out of space in /var ,
Resolution: please make sure /var/log is running in its own partition, specially especially if you increased Swarm log levels, free up space and you should then be able to start avahi-daemon.