easymp3gain-gtk: 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/lib/debug/usr/bin/easymp3gain-gtk - from package: easymp3gain-dbg
/usr/bin/easymp3gain-gtk - from package: easymp3gain-gtk

You may install the required package with command apt-get install {package}
Error in other languages:
easymp3gain-gtk: bevel nie gevind nie
easymp3gain-gtk: comandă negăsită
easymp3gain-gtk: comando não encontrado
easymp3gain-gtk: commande introuvable
easymp3gain-gtk: command not found
easymp3gain-gtk: käsku ei ole
easymp3gain-gtk: không tìm thấy lệnh
easymp3gain-gtk: komanda nerasta
easymp3gain-gtk: Kommando nicht gefunden.
easymp3gain-gtk: kommandot finns inte
easymp3gain-gtk: komut yok
easymp3gain-gtk: nie znaleziono polecenia
easymp3gain-gtk: níor aimsíodh an t-ordú
easymp3gain-gtk: no se encontró la orden
easymp3gain-gtk: no s'ha trobat l'ordre
easymp3gain-gtk: opdracht niet gevonden
easymp3gain-gtk: parancs nem található
easymp3gain-gtk: perintah tidak ditemukan
easymp3gain-gtk: príkaz nenájdený
easymp3gain-gtk: příkaz nenalezen
easymp3gain-gtk: команда не найдена
easymp3gain-gtk: командата не е открита
easymp3gain-gtk: 命令找不到
easymp3gain-gtk: コマンドが見つかりません