@AVLfilm 

Thanks for all the thoughts in this thread. I had to change our WiFi password after setting up a new Xfinity modem/router. Xfinity decided the special symbol (a pretty normal one) I used in my WiFi password is no longer on their list of acceptable symbols.  So, I changed the WiFi password.

I'm dealing with what everybody else here is dealing with.  But I think I'm doing something wrong.  I hold the device reset button for 5 seconds and the lights blink but other than adding a new device to the Kasa app, I don't see how to enter the new password.

Or, is the idea to remove one of my many devices, add it like a new device, and I'll be asked to enter the new password and, after that, all the other TP-Link devices will work?

It sounds like there is a solution other than manually removing and adding each device separately. I'm just having trouble understanding how to do that.

Sincere thanks, everybody (anybody!).

  @cgulls  . . . also, how do reset a lightbulb?  The smart plugs have reset buttons but the bulbs don't. 

Thanks!

  @cgulls Sounds like you're only doing half of what you need to. After you hold the device reset button for 5 seconds and the lights blink, click + like you're adding a new device. Connect to the device following the instructions on your screen. Then choose "Do Not Reset". Choose the new wifi network and enter password. That's it. It might automatically update the firmware on the plug too.