monav-preprocessor-gui: 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/monav-preprocessor-gui - from package: monav-preprocessor

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

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