@eight,

I would recommend trying to use the IP of the device, as it does not require a redirect and is often more consistent. I was able to find this FAQ, How to Login to the Web-Based Interface on Your TP-Link Range extender, which includes instructions to verify that the IP given to the laptop is correct.

When the RE's are operating in Access Point Mode, the RE can only be reached when the phone/laptop is on the same segment of the your network. For this reason, the easiest way to do this is to wire a laptop directly to the Range Extender. This also applies to the Tether App, so if your device was not connected/communicating via the Range Extender, the Tether app would not see the device in AP mode; and it is also worth mentioning that some REs do not support the tether app while they are operating in AP mode; so it may be best to use the WebUi until you know if the RE650 supports Tether in AP mode.

  @eight,

Glad you got everything figured out. The IP address is always the best way to connect to our devices as it does not have to be translated or redirected, rather it establishes a direct link with the RE. For future info, the Router's Client List is not the only way to get the IP address of the device, you can also do so through a client computers network adapter.

How to log into the Web GUI of my Range Extender via IP address or domain name