@Cuna 

Hi, have you ever tried to set up the extender? If not, please refer to the instructions below to configure it:
Via Tether App: https://www.tp-link.com/support/faq/1373/

Via Web interface: https://www.tp-link.com/support/faq/1400/

You could refer to the link below to check if it has been configured successfully and if it is in a proper location:
https://www.tp-link.com/support/faq/2692/

If there is still any problem, please share with me details of the problem, model number, hardware version and LED status on the extender.