vpnc-connect: 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/sbin/vpnc-connect - from package: vpnc

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

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