All clients gone offline

OS: OpenMediaVault (debian10)

So my issue is, some time ago my /var folder goes completely full, and crashed my whole server, after cleaning /var i rebooted my server and all what i see is all of my urbackup clients are gone offline, what should i do now?

Maybe try to restore /var/urbackup from the backup location? (/[urbackup_storage_location]/urbackup). Just copy the files over. Make sure the service is stopped.