simplify2why: 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/simplify2why - from package: why

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

Error in other languages:
simplify2why: bevel nie gevind nie
simplify2why: comandă negăsită
simplify2why: comando não encontrado
simplify2why: commande introuvable
simplify2why: command not found
simplify2why: käsku ei ole
simplify2why: không tìm thấy lệnh
simplify2why: komanda nerasta
simplify2why: Kommando nicht gefunden.
simplify2why: kommandot finns inte
simplify2why: komut yok
simplify2why: nie znaleziono polecenia
simplify2why: níor aimsíodh an t-ordú
simplify2why: no se encontró la orden
simplify2why: no s'ha trobat l'ordre
simplify2why: opdracht niet gevonden
simplify2why: parancs nem található
simplify2why: perintah tidak ditemukan
simplify2why: príkaz nenájdený
simplify2why: příkaz nenalezen
simplify2why: команда не найдена
simplify2why: командата не е открита
simplify2why: 命令找不到
simplify2why: コマンドが見つかりません