MSSimulator: 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/MSSimulator - from package: topp

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

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