@Padre2,

Is it possible the devices are trying to reconnect to your network with the 5Ghz band? I would recommend trying to set them up on your guest network (make sure network device discovery is on in the router settings if doing so). 

Otherwise, I would recommend trying a soft reset of the smart plugs, as you have already completed a factory reset. If you hold the button for 5 seconds compared to the whole 10 seconds for a factory reset, the plug will reset its network connection but keep its settings. This may allow you to connect the device back into the network.

  @Padre2,

First, what is your home network look like? What brand of router do you have and what model? it looks like there are certain settings from manufacturers that could be interfering with the connection. 

Also, When the devices are set to be local only, what is the color of the LED light on the plug?

On your router, Disable Fast Roaming if using a Mesh Setup.

If your router supports firewall levels(high/medium/low), change to either medium or low during the configuration process, you can change it back after the setup process.

The first general troubleshooting step is to look in your router settings for AP Isolation/Client Isolation and Toggle the Setting.

Try Changing the Security Setting away from WPA/WPA2 to simply WPA2

Another thing that a lot of users have done for troubleshooting is to setup their smart plugs on their guest network.