@duarte_teixeira
Please try factory reset range extender again, and see if it brocast Range exntederXX, or Extender XX wifi on the phone, laptop?
- RESET: With the extender powered on, use a pin to press the RESET button (pinhole) until all the LEDs flash once.
- Try a different power outlet and confirm its not poor contact with the power socket
Here is a Configuration Guide that you may need after reset: TP-Link Range Extender Setup (Range Extender Mode)