wpd2epub: 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/wpd2epub - from package: wpd2epub

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

Error in other languages:
wpd2epub: bevel nie gevind nie
wpd2epub: comandă negăsită
wpd2epub: comando não encontrado
wpd2epub: commande introuvable
wpd2epub: command not found
wpd2epub: käsku ei ole
wpd2epub: không tìm thấy lệnh
wpd2epub: komanda nerasta
wpd2epub: Kommando nicht gefunden.
wpd2epub: kommandot finns inte
wpd2epub: komut yok
wpd2epub: nie znaleziono polecenia
wpd2epub: níor aimsíodh an t-ordú
wpd2epub: no se encontró la orden
wpd2epub: no s'ha trobat l'ordre
wpd2epub: opdracht niet gevonden
wpd2epub: parancs nem található
wpd2epub: perintah tidak ditemukan
wpd2epub: príkaz nenájdený
wpd2epub: příkaz nenalezen
wpd2epub: команда не найдена
wpd2epub: командата не е открита
wpd2epub: 命令找不到
wpd2epub: コマンドが見つかりません