@PSG100 

Hi,

Please try again.

First "Reset" the RE300. (marked "1" in the picture taken from the user manual below)

Then wait a minute or two for the RE300 to boot up again.

Then perform the step marked "2".

 Hi @PSG100,

Via the WPS button, there is a physical WPS button on the Range Extender. Press the WPS button on the Router, and the Range Extender in turn. The Range Extender will connect to the Router automatically within 2 minutes. If the router doesn't have a WPS button, you may try the other two methods instead. For detailed instructions, please refer to:

Configure my Range Extender via WPS button

Alternatively, here is a full setup video for your reference:

How to set up a TP-Link Range Extender