@Snowbie1 

A few things worth checking would be:

1. After receiving the "couldn't connect" message, does the smart plug's LED continue to flash orange and green?

2. When you receive the connection message, is your iPhone reconnected to your router's Wi-Fi network?

3. Is your EP40 located in an area where your router's 2.4 GHz Wi-Fi network signal is sufficiently strong/stable?

4. Is your smartphone connected to a VPN? If so, please disconnect from the VPN during setup, as it will interfere with the installation process.

I would also make sure your Kasa app is fully up to date, if it isn't already.

  @Snowbie1 I'm having the same problem. I purchased one of the smart plugs and had no problems connecting it. I have purchased a second one and can't seem to connect it to the app where my other plug is already added. Did you ever get any resolution

  @Ryan I have the same exact problem! All the same. I am connected to the router correctly, no VPN, blinking blue and orarnge and I just get the spinning circle and then a message to try again.

  @MZ404  

@ Ryan..  called customer support and they were very helpful.  I was missing one very important step.  The step where when it pops up WiFi and tp-link, go to your settings and ensure you are on your WiFi, then look below at the other WiFi choices, find Direct TP-device, click on it to link your device to your home WiFi, type in your WiFi password, then proceed with the rest of instructions.  If that's not clear, call customer support. Hope it helps. 

  @Tracy7012