7za: 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 CentOS possible default full paths are:

/usr/bin/7za - from package: p7zip

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/7za - from package: p7zip-full

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

Error in other languages:
7za: bevel nie gevind nie
7za: comandă negăsită
7za: comando não encontrado
7za: commande introuvable
7za: command not found
7za: käsku ei ole
7za: không tìm thấy lệnh
7za: komanda nerasta
7za: Kommando nicht gefunden.
7za: kommandot finns inte
7za: komut yok
7za: nie znaleziono polecenia
7za: níor aimsíodh an t-ordú
7za: no se encontró la orden
7za: no s'ha trobat l'ordre
7za: opdracht niet gevonden
7za: parancs nem található
7za: perintah tidak ditemukan
7za: príkaz nenájdený
7za: příkaz nenalezen
7za: команда не найдена
7za: командата не е открита
7za: 命令找不到
7za: コマンドが見つかりません