mmroff: 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/mmroff - from package: groff-perl

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

On Debian possible default full paths are:

/usr/bin/mmroff - from package: groff

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

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