fprobe: 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/sbin/fprobe - from package: fprobe

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

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