Please try to factory reset the extender by press the reset button on the back for 8-10 seconds agian, you will see the screens changes when you do that. 

After reset, please connect to the extender's wifi on your phone or computer, then open a web browser and type in 192.168.0.254 or tplinkrepeater.net in the address bar, hit enter, the admin login page will show up. If it is not working, please try different browsers and devices. 

And you can also check the IP address on your phone or computer, the default gateway should be 192.168.0.254. 

I have found that the most reliable way to connect to the repeater for setup is to use an ethernet cable to your laptop and do it via LAN.

Should you choose to do it wirelessly, make sure you disconnect yourself manually from any other WiFi and connect manually to the TP-Link one.

Just to be sure the problem is not with your browser, either use an incognito window or clear your data and cookies before trying to connect. Incognito is a far easier solution.

In sum: connect to the repeater via ethernet, open an incognito window on Chrome, type tplinkrepeater.net and proceed with the setup.

I hope it helps.