TP-Link Wifi extender suddenly won't connect the internet to my MacBook Pro

Hi all,

About two days ago my MacBook Pro decided to stop being able to connect to the internet using the TP-Link AC1200 WiFi Extender (RE300). It appears to be connected (the wifi symbol is filled in/turned on) but the internet is not working.

Nothing changed, no one touched the extender and I have no idea what happened. I live alone and unless my Pomeranian decided to become a hacker there is no good reason why this should be an issue. I spent hours today trying to deal with TP-Link tech support and it was not a good experience. 

Relevant Info:

• My MacBook Pro is an A1990.
• I have tested the main wifi (the one I'm extending since it's spotty at times) and it works fine.
• I have also tried using the extender with my various gadgets and no issues there (both the extender wifi and the main wifi work fine). I've tested the wifi extender on my Android phone, iPad tablet, another MacBook Pro, a Dell Windows laptop, a few Google Nests/Minis and two Roku TVs. Everything is working.
• TP-Link Model: RE300 / Hardware Version: V1 / Firmware Version: 1.0.5 Build 20191114 Rel. 34543

I live in the basement of a house so I have no option for wired internet (to mess with a router) and I'm reluctant to reset the extender as I'd have to deal with my landlord and get into her office to get it talking to the extender again. Plus I don't want to mess up all the other gadgets in my house as everything else is currently working. I'd do it as a last resort but I'm thinking this may be a Mac issue? Not sure.

I've tried a few things including:

• Taking the extender out for a few minutes and plugging it back in. No dice.
• Removing the extender wifi network option from the list of available networks (xxx_EXT) to connect to and reconnecting it. No dice.
• Wiping the wifi settings from the Mac. No dice.

I'd appreciate any suggestions as it appears that it's my MacBook Pro but I don't know how to get the two talking and working again.

Thanks!