wps2epub: command not found

Have You tried accessing the binary with the full path?

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/wps2epub - from package: wps2epub

You may install the required package with command apt-get install {package}
Error in other languages:
wps2epub: bevel nie gevind nie
wps2epub: comandă negăsită
wps2epub: comando não encontrado
wps2epub: commande introuvable
wps2epub: command not found
wps2epub: käsku ei ole
wps2epub: không tìm thấy lệnh
wps2epub: komanda nerasta
wps2epub: Kommando nicht gefunden.
wps2epub: kommandot finns inte
wps2epub: komut yok
wps2epub: nie znaleziono polecenia
wps2epub: níor aimsíodh an t-ordú
wps2epub: no se encontró la orden
wps2epub: no s'ha trobat l'ordre
wps2epub: opdracht niet gevonden
wps2epub: parancs nem található
wps2epub: perintah tidak ditemukan
wps2epub: príkaz nenájdený
wps2epub: příkaz nenalezen
wps2epub: команда не найдена
wps2epub: командата не е открита
wps2epub: 命令找不到
wps2epub: コマンドが見つかりません