Luiz, you haven't told us what device your using..
Is it an IOS, or 'Droid, or Tablet ??
And are you letting the 'app' do the download ??
If you look on YT (youtube), there are vids that cover
how to do it. I would suggest trying "Tello Firmware
Update" That may take you right to the one your
Good luck, and let us know how it went..
Welcome to the fun.....