mp3cue: command not found

Have You tried accessing the binary with the full path?

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/mp3cue - from package: poc-streamer

You may install the required package with command apt-get install {package}
Error in other languages:
mp3cue: bevel nie gevind nie
mp3cue: comandă negăsită
mp3cue: comando não encontrado
mp3cue: commande introuvable
mp3cue: command not found
mp3cue: käsku ei ole
mp3cue: không tìm thấy lệnh
mp3cue: komanda nerasta
mp3cue: Kommando nicht gefunden.
mp3cue: kommandot finns inte
mp3cue: komut yok
mp3cue: nie znaleziono polecenia
mp3cue: níor aimsíodh an t-ordú
mp3cue: no se encontró la orden
mp3cue: no s'ha trobat l'ordre
mp3cue: opdracht niet gevonden
mp3cue: parancs nem található
mp3cue: perintah tidak ditemukan
mp3cue: príkaz nenájdený
mp3cue: příkaz nenalezen
mp3cue: команда не найдена
mp3cue: командата не е открита
mp3cue: 命令找不到
mp3cue: コマンドが見つかりません