@daaveh 

Hi,

If your TP-Link router is a somewhat recent model that supports OneMesh/EasyMesh, but you want your RE550 to have SSIDs that are separate from the SSIDs of your TP-Link router, then make sure you switch OneMesh/EasyMesh OFF on your RE550, as otherwise you will end up with a seamless Mesh network between the RE550 and the TP-Link router in which the SSIDs of the RE550 will become identical to the SSIDs of the Wi-Fi router.
 

  @woozle Hi, thanks for the reply.

I turned EasyMesh off on the extender but that didn’t solve the issue.

  @woozle Interesting—the SSIDs are the same as my router’s. So I can just rename the extended 2.4GHz/5GHz SSIDs to anything as long as they’re identical, e.g. “Extender,” or what I renamed the RE550?

  @daaveh 

The device name that the Tether app shows you (like "RE550") is unrelated to the names of the wireless networks. You can name the Extended networks whatever you like. Whatever you enter in the two "Extended x GHz SSID" fields is what your will see when you search for nearby networks on your wireless client devices.

  @woozle That worked! All devices can see the extender now—however: The password to connect isn’t being accepted; I’m informed a WPA2 password is required which, of course, I have and it’s the right pwd. I rebooted the RE550 and this new hiccup persists.

Within macOS network settings it says No IP Address when I attempt connection to the RE550, which I really don’t think is accurate.

Figured it out!

Thank you so much for your help, Woozle. If I can tip you via PP or something please let me know.