monop: 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/monop - from package: mono-devel

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

On Debian possible default full paths are:

/usr/bin/monop - from package: mono-devel

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

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