upnpc: 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/upnpc - from package: miniupnpc

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

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