mptoggle: 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/mptoggle - from package: mpdtoys

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

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