pnscan: command not found

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

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

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/bin/pnscan - from package: pnscan

You may install the required package with command apt-get install {package}

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