mkvpropedit: 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 CentOS possible default full paths are:

/usr/bin/mkvpropedit - from package: mkvtoolnix

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/mkvpropedit - from package: mkvtoolnix

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

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