txt2pbes: 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/txt2pbes - from package: mcrl2

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

Error in other languages:
txt2pbes: bevel nie gevind nie
txt2pbes: comandă negăsită
txt2pbes: comando não encontrado
txt2pbes: commande introuvable
txt2pbes: command not found
txt2pbes: käsku ei ole
txt2pbes: không tìm thấy lệnh
txt2pbes: komanda nerasta
txt2pbes: Kommando nicht gefunden.
txt2pbes: kommandot finns inte
txt2pbes: komut yok
txt2pbes: nie znaleziono polecenia
txt2pbes: níor aimsíodh an t-ordú
txt2pbes: no se encontró la orden
txt2pbes: no s'ha trobat l'ordre
txt2pbes: opdracht niet gevonden
txt2pbes: parancs nem található
txt2pbes: perintah tidak ditemukan
txt2pbes: príkaz nenájdený
txt2pbes: příkaz nenalezen
txt2pbes: команда не найдена
txt2pbes: командата не е открита
txt2pbes: 命令找不到
txt2pbes: コマンドが見つかりません