lpssim: 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/lpssim - from package: mcrl2

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

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