sncancel: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/sbin/sncancel - from package: sn

You may install the required package with command apt-get install {package}
Error in other languages:
sncancel: bevel nie gevind nie
sncancel: comandă negăsită
sncancel: comando não encontrado
sncancel: commande introuvable
sncancel: command not found
sncancel: käsku ei ole
sncancel: không tìm thấy lệnh
sncancel: komanda nerasta
sncancel: Kommando nicht gefunden.
sncancel: kommandot finns inte
sncancel: komut yok
sncancel: nie znaleziono polecenia
sncancel: níor aimsíodh an t-ordú
sncancel: no se encontró la orden
sncancel: no s'ha trobat l'ordre
sncancel: opdracht niet gevonden
sncancel: parancs nem található
sncancel: perintah tidak ditemukan
sncancel: príkaz nenájdený
sncancel: příkaz nenalezen
sncancel: команда не найдена
sncancel: командата не е открита
sncancel: 命令找不到
sncancel: コマンドが見つかりません