txt2ti3: 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/txt2ti3 - from package: argyll

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

Error in other languages:
txt2ti3: bevel nie gevind nie
txt2ti3: comandă negăsită
txt2ti3: comando não encontrado
txt2ti3: commande introuvable
txt2ti3: command not found
txt2ti3: käsku ei ole
txt2ti3: không tìm thấy lệnh
txt2ti3: komanda nerasta
txt2ti3: Kommando nicht gefunden.
txt2ti3: kommandot finns inte
txt2ti3: komut yok
txt2ti3: nie znaleziono polecenia
txt2ti3: níor aimsíodh an t-ordú
txt2ti3: no se encontró la orden
txt2ti3: no s'ha trobat l'ordre
txt2ti3: opdracht niet gevonden
txt2ti3: parancs nem található
txt2ti3: perintah tidak ditemukan
txt2ti3: príkaz nenájdený
txt2ti3: příkaz nenalezen
txt2ti3: команда не найдена
txt2ti3: командата не е открита
txt2ti3: 命令找不到
txt2ti3: コマンドが見つかりません