kdenlive_render: 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/kdenlive_render - from package: kdenlive

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

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