nntp-get: 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
/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/nntp-get - from package: sinntp

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