Hello   @Lakhad 

RE450 should have Power led, or 2.4Ghz/5Ghz LED light up after it successfully to a Wi-Fi router. 

If only power Led is solid blue, you could factory reset the range extender as below thread and see if extender respond to a factory reset? 

TP-Link Range Extender Setup (Range Extender Mode)

Please check if the range extender still broadcast the extender Wi-Fi SSID after the reset, if yes, try to set up your range extender as the above configuration guide.