mate-wm: 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/mate-wm - from package: mate-session-manager

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

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