stl2gts: 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/stl2gts - from package: libgts-bin

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

Error in other languages:
stl2gts: bevel nie gevind nie
stl2gts: comandă negăsită
stl2gts: comando não encontrado
stl2gts: commande introuvable
stl2gts: command not found
stl2gts: käsku ei ole
stl2gts: không tìm thấy lệnh
stl2gts: komanda nerasta
stl2gts: Kommando nicht gefunden.
stl2gts: kommandot finns inte
stl2gts: komut yok
stl2gts: nie znaleziono polecenia
stl2gts: níor aimsíodh an t-ordú
stl2gts: no se encontró la orden
stl2gts: no s'ha trobat l'ordre
stl2gts: opdracht niet gevonden
stl2gts: parancs nem található
stl2gts: perintah tidak ditemukan
stl2gts: príkaz nenájdený
stl2gts: příkaz nenalezen
stl2gts: команда не найдена
stl2gts: командата не е открита
stl2gts: 命令找不到
stl2gts: コマンドが見つかりません