Are you looking to for better performance, or are you trying to unlock it to install your own apps?
After a download completes, the box will usually prompt for a manual reboot to apply the new software. Manual & Third-Party Firmware Support technicolor dwi259s firmware download
If a valid firmware binary is obtained, the installation process generally bypasses the TR-069 method and utilizes the local web interface or a recovery mode. Are you looking to for better performance, or
If you want, I can summarize steps to safely obtain firmware for a Technicolor DWI259S (official channels to try, precautions when flashing, and what to avoid). precautions when flashing
If you suspect your DWI259S is stuck on old firmware, you can force a check without downloading anything: