@richardgeraldy 

Hi, please check LED status on the TL-WA854RE now especially the RE led and signal strength LEDs, if they are not on yet, it means the extender is not connected to your router now, please check whether Wireless password of your new router you entered is correct or not. 

You could go to Settings--WiFi on your phone to forget the new router WiFi, then reconnect it using the same Wi-Fi password to see if it works. 

After that, please reset the extender into default settings again by holding the reset button until all lights flashing once, then refer to this instruction to configure your range extender again carefully:

Via Tether App: https://www.tp-link.com/support/faq/1373/
Via Web interface: https://www.tp-link.com/support/faq/1400/

However, if RE and signal strength LEDs have already been on, but no internet access from the extended network, please connect a client device to the extended network, then check IP address, subnet mask and default gateway of the client device to see if the IP address is assigned by the router or not.

How to find IP address on your devices

  @richardgeraldy 

Thanks for the update, glad to hear that it is working now.