I had strange things with a router when my UPS went bad. May want to try a different power source. But it sounds like it may be "bricked". There are instructions on the internet for un-bricking some...

Try the 30-30-30 reset... Sometimes it works... https://www.router-reset.com/30-30-30-reset-factory-defaults-wireless-router/

Another thought.. Can you sign on to the router remotely using your IP address plus the port number ( something like 55.55.55.555:8080)?

see https://static.tp-link.com/2018/201802/20180224/1910012180_Archer%20C1200_UG.pdf

see https://www.tp-link.com/us/faq-1366.html

I agree. it would be nice to be able to sort the list by MAC or by assigned IP.