gnatpp: 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/gnatpp - from package: asis-programs

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

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