gts2stl: command not found

Have You tried accessing the binary with the full path?

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/gts2stl - from package: libgts-bin

You may install the required package with command apt-get install {package}
Error in other languages:
gts2stl: bevel nie gevind nie
gts2stl: comandă negăsită
gts2stl: comando não encontrado
gts2stl: commande introuvable
gts2stl: command not found
gts2stl: käsku ei ole
gts2stl: không tìm thấy lệnh
gts2stl: komanda nerasta
gts2stl: Kommando nicht gefunden.
gts2stl: kommandot finns inte
gts2stl: komut yok
gts2stl: nie znaleziono polecenia
gts2stl: níor aimsíodh an t-ordú
gts2stl: no se encontró la orden
gts2stl: no s'ha trobat l'ordre
gts2stl: opdracht niet gevonden
gts2stl: parancs nem található
gts2stl: perintah tidak ditemukan
gts2stl: príkaz nenájdený
gts2stl: příkaz nenalezen
gts2stl: команда не найдена
gts2stl: командата не е открита
gts2stl: 命令找不到
gts2stl: コマンドが見つかりません