mp3check: 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/mp3check - from package: mp3check

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

Error in other languages:
mp3check: bevel nie gevind nie
mp3check: comandă negăsită
mp3check: comando não encontrado
mp3check: commande introuvable
mp3check: command not found
mp3check: käsku ei ole
mp3check: không tìm thấy lệnh
mp3check: komanda nerasta
mp3check: Kommando nicht gefunden.
mp3check: kommandot finns inte
mp3check: komut yok
mp3check: nie znaleziono polecenia
mp3check: níor aimsíodh an t-ordú
mp3check: no se encontró la orden
mp3check: no s'ha trobat l'ordre
mp3check: opdracht niet gevonden
mp3check: parancs nem található
mp3check: perintah tidak ditemukan
mp3check: príkaz nenájdený
mp3check: příkaz nenalezen
mp3check: команда не найдена
mp3check: командата не е открита
mp3check: 命令找不到
mp3check: コマンドが見つかりません