@sakymare Good day, 

From your description the device should be defective on its hardware, you could try another factory reset, if it does not work, you could check warranty with retailer/ local support or consider purchase a new range extender. 

RESET: With the extender powered on, use a pin to press the RESET button until most Leds flash once. 

Hello@sakymare 

Could your laptop or phone see the WiFi from range extender, if yes, please check what is the IP address when connected to wifi extender?

It extender still gives out IP address 192.168.0.X, the device is probably not faulty yet.  If its device could not connect to extender wifi , you could check device warranty. 

You could follow the instrucions here to set up range extender :
（How to configure Range Extender via Tether APP）https://www.tp-link.com/support/faq/357/
（How to configure my range extender via web GUI to extend an existing wireless network's coverage）https://www.tp-link.com/support/faq/1400/

If the the Signal Leds are OFF, you could verifry wifi password and follow the guide to troubleshoot: 

Has connected to TP-Link extender but no internet, what can I do?
https://community.tp-link.com/en/home/forum/topic/198516