I have three Tp-link devices, two smart bulbs and the plug that's stopped responding. The bulbs (and the 12 other devices attached to my router) are working fine. I'm loath to start changing any settings as all the other devices are OK. I didn't use it very much anyway...I can manage without it.

  @Ray_M I have the same problem!  There are no responses that help.

  @SBM1950 

Or perhaps none simple enough you like them?  

Have you factory reset (not reboot) the switch yet?

What is the MAC id of the switch in question?

What does the correlating system log in the Router show?

Have you taken the above and used a mac reservation?

Once you've found it and confirmed you know it's pulled an IP address, can you ping it?

What channel are you using on the Wifi?

What is signal db on phone when held right next to affected plug?

If you turn off literally everything in the house that uses 2.4 Wifi except for that plug, what does it do?

It's really relatively simple.  If there is nothing interfering logically or physically, and the above will isolate all that, then as simple as replacing it.