plog: 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/plog - from package: ppp

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

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