Thank you for the reply @terziyski Really appreciate it. The info at the link you provided didn't show me the solution to my specific question (at least it wasn't obvious to me).

However I did resolve the issue last night. Its really simple (not sure why I didn't do this the first time!).

Issue:

The first TL-WA854RE was already successfully setup. But it was interfering with the setup of the second TL-WA854RE. This is because the the default credentials are the same for both units.

Solution:

* Ensure the first TL-WA854RE is setup correctly

* Unplug the first TL-WA854RE (SSD "[mynetworkname]_EXT")

* Setup the second TL-WA854RE

* During the setup for the second unit, change the SSD to [mynetworkname]_EXT2 (it can be any SSD - you choose)

* Plug the First Unit Back in.

Result:

Each TL-WA854RE now has its own SSD Connect your clients/devices to either _EXT or _EXT2
(Remember to connect your phone to the appropriate SSD during this process)

Notes:

* These devices only seem to be able to handle 12 clients/devices.So split your devices appropriately.

* You should be able to see the signal strength in the native app for the device you are connecting to your range extender (at least I could for my devices)

* Once your all setup you can connect your phone/laptop back to the main network [mynetworkname] and you'll be able to see both of your range extenders in the Tether app.

* if you can't see both range extenders in the tether app its probably because the device you are using the Tether app on is directly connected to one of the range extenders (see previous bullet point)