@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)