@scynth 

Hello, what is the model number of your range extender? How about the lights on it?

If all the lights are correctly on, which means the extender should be set up successfully and you may check if you have got the IP address when connecting the computer to it.

If the RE light is not correctly on, please follow the below instructions to reconfigure it:

What should I do if I fail to configure TP-Link Range Extender?

May this help.