iptables-apply: 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/iptables-apply - from package: iptables

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

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