Can't find a thing on it. I have 3 HS100s and 2 HS200 which worked perfectly up until tonight. Now my Echo Dot says either "device not responding " or "that command does not work with this device" Seems a lot of people are experiencing the same problem.

Wish I did. When I left for work (approx. 0800 US Eastern), they were responding to my Echo Dots without issue, using the Kasa Skill. As they have since I first started installing them (60 days ago +/-) Got home this evening (approx. 1700 US Eastern), and they were almost completely unresponsive. Disabled Kasa Skill, now it will not log back into Amazon account. Kasa still controls the lights by itself.

I'm wondering if it's a "leftover" from the Amazon outage earlier this week. Fix one bug and introduce two more - which crop up at less than desirable times.....

Echo Dots appear to have no other issues (at least for me) other than this one.

I agree, nothing makes sense. I suspect a firmware upgrade but I don't know which device may have gotten it. I can control the devices locally, but not with Alexa. But the devices behave strangely - when I tried to turn Remote off and on, they get errors, and either the KASA app or the devices report that they don't have network. But clearly they do since I can control them, and the network lights are green. I'm thinking something on the TP-Link side of things.

I agree with you.
I see my two smart plugs register to my wireless network, receive IP address, can ping, but IOS app and Alexa wont recognize.

Same here very frustrating as I just set up several more and bought some.

I'm having the same issues, when trying to reauthorize alexa to kasa, I keep getting server internal error and it's not getting in.

It seems you are correct.

I've had the problem all day 3-2, and it was the same all day 2-28.

Noticed same problem, but no idea what's up....or what's not.
Some devices went online for a short time, but then went back to local.

I've had the problem all day 3-2, and it was the same all day 2-28.