mcxassemble: 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/mcxassemble - from package: mcl

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

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