mp3diags: 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/mp3diags - from package: mp3diags

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

Error in other languages:
mp3diags: bevel nie gevind nie
mp3diags: comandă negăsită
mp3diags: comando não encontrado
mp3diags: commande introuvable
mp3diags: command not found
mp3diags: käsku ei ole
mp3diags: không tìm thấy lệnh
mp3diags: komanda nerasta
mp3diags: Kommando nicht gefunden.
mp3diags: kommandot finns inte
mp3diags: komut yok
mp3diags: nie znaleziono polecenia
mp3diags: níor aimsíodh an t-ordú
mp3diags: no se encontró la orden
mp3diags: no s'ha trobat l'ordre
mp3diags: opdracht niet gevonden
mp3diags: parancs nem található
mp3diags: perintah tidak ditemukan
mp3diags: príkaz nenájdený
mp3diags: příkaz nenalezen
mp3diags: команда не найдена
mp3diags: командата не е открита
mp3diags: 命令找不到
mp3diags: コマンドが見つかりません