I am having the same error tried all the things here and nothing works. I have been using this switch for quite sometime, I would return it if I could. Any solutions here?

This is caca!!!!!!!!!!!, on the balls of these fucking plugs ... more than € 100 wasted in the trash ... very good TPLINK "NEVER AGAIN"

@2na - what does this even mean?  "Renamed it in my router" .... ????   Gave it a new DNS PTR record? 

At any rate - I'm getting this error with one of my devices now and I've tried everything suggested ... updated PTR record for local DNS entry, forced in DHCP server settings to a new IP Address, removed / reset to factory default / re-add to app, log out of app/back in, etc.  Still no luck.  Always "another cmd is running" when trying to enable remote control. 

Absolutely maddening.  I'd like TP-Link to send me a new outlet, the one that's giving me the "another cmd is running" error is nearly a paperweight to me at this point.

@Liztplink I had this same issue with the HS100 plug I use for my Christmas tree. I put it away last January and took it back out today. Could not control with Alexa anymore nor discover it after resetting it back to factory defaults and reconfiguring. I aso got the same cmd is running error when I tried to enable remote control. The only thing I could do is turn on or off through TP-Link app. I renamed it in the router as someone else suggested but that did not work. What worked for me was rebooting my router (I have a Netgear Nighthawk router). Once the router came back up I got  notification on my phone saying the plug "is connected to Alexa with the TP-LINK Kasa skill". And remote control is automatically enabled. It works again! Reboot your router!

@SusiFT reboot your router.