po4a: 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/po4a - from package: po4a

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

On Debian possible default full paths are:

/usr/bin/po4a - from package: po4a

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

Error in other languages:
po4a: bevel nie gevind nie
po4a: comandă negăsită
po4a: comando não encontrado
po4a: commande introuvable
po4a: command not found
po4a: käsku ei ole
po4a: không tìm thấy lệnh
po4a: komanda nerasta
po4a: Kommando nicht gefunden.
po4a: kommandot finns inte
po4a: komut yok
po4a: nie znaleziono polecenia
po4a: níor aimsíodh an t-ordú
po4a: no se encontró la orden
po4a: no s'ha trobat l'ordre
po4a: opdracht niet gevonden
po4a: parancs nem található
po4a: perintah tidak ditemukan
po4a: príkaz nenájdený
po4a: příkaz nenalezen
po4a: команда не найдена
po4a: командата не е открита
po4a: 命令找不到
po4a: コマンドが見つかりません