I am guessing the issue is actually with those Leviton Z-Wave switches/dimmers. There is a known issue with Leviton devices NOT reporting there status updates back to the hub. To fix this issue, a firmware upgrade on the Leviton switches is necessary.
There are numerous threads regarding these Leviton switches. A simple search turned up this one which seems to have quite a bit on information in it regarding how to upgrade the switches.
Thank you. I will try that. it is definitely better than replacing all of my switches and dimmers.
I would like to report that upgrading the firmware on all of the Leviton devices has fixed the issue. I had given up on finding firmware a while back on ST since OTA was not supported. HomeSeer Z-Flash kit worked like a charm. Thanks ogiewon!
Great the virus has spread and now i have it! Moved all my devices from US account to Au account. Basically a "fresh install" from an Amazon perspective. I'm using the Skill and reinstalled that too.
All my connected HE connected devices trigger the "not responding" even though they work fine. Anything external to the HE works fine on Alexa, so got to be an HE thing.
It's a real nuisance as many have said, "the regular people" in our family were getting used to the whole automation thing and are now losing confidence!
Any suggestions?
Did you remove the Amazon Echo Skill App from Hubitat before switching to the AU Alexa account? Just wondering if there is something left over from the previous installation/configuration.
Dan can we promote you from Ambassador to demigod ..... here's how i fixed it and not sure what the fix piece was, I hadn't tried scorched earth on everything at once and a reboot:
All fixed ....... for now at least. I'd done all of these elements before but not 1,2,3 all at once.
Cheers
Mike
Nice! Glad to hear you got it behaving. Hopefully the family confidence is restored! 
I am having the same issue. Peanut using Generic Zigbee Outlet. Works fine but Alexa reports that it is not responding.
When you view the Peanut Plug's device details page in Hubitat, does the STATUS change from "on" to "off" and vice versa when you press the ON and OFF buttons on the same page? If not, click CONFIGURE, wait a few seconds and try again. If it still does not update in a timely manner, then we'll need to talk about what types of other Zigbee devices are on your network, especially Zigbee bulbs. Many of them are poor Zigbee repeaters and cause issues like the one you're experiencing.
One more thing... In the list of Hubitat Apps you have installed, are you using the "Amazon Echo Skill" or the "Amazon Echo App"? You should be using the "Amazon Echo App" which is automatically installed on your Hubitat Hub when "Enable the Hubitat Skill" from within the Amazon Alexa mobile phone app.
Thanks Ogiewon - that was the issue. It was showing state but not updating. Ran configure again and everything is working.
This worked for me. But I'm wondering how often do I have to do this? I've only had the hubitat a few days and never had to do this before with my smartthings hub.
This should be only a one-time thing. Hubitat made some major changes to the Alexa Hubitat Skill in a recent release. This was the only time that I know of that caused a couple of users to need to go through this process. Hopefully it will be the last time! 
I've only had to do it the once, was due to change of accounts I think!
Just wanted to mention that I experienced this exact issue -- with Alexa turning off a room with a generic Zigbee smart switch and a Hue light -- and then saying that the device was not responding.
I removed the skill and the Alexa Skill from HE, then re-added and re-linked and now things are working fine.
When things are fixed, Alexa gives the proper little "blorp-blorp" sound (for lack of a better description 
when the room is turned on. Before, with the problem, you never heard the blorp-blorp. Probably because Alexa was waiting for an "OK done" it for some reason never received from HE.
+1 here .. i also have this issue just starting in the last few days. Commenting to follow the thread for a possible fix.
this issue has suddenly reappeared since Saturday.
started getting this issue back in the last 2 days, made no system/device updates.
Check the device details page on your Hubitat Hub for the device in question. While watching that page, use Alexa to change the state of the device. Does the state change instantly on the Hub's Device Details page for that device? If not, that is the issue, not the Alexa Skill. The Alexa Skill reports the "device is not responding" when the hub fails to tell Alexa that the device has changed states within a timeout period.
Anyone get resolution to this? I removed the Alexa Skill and readded. This fixed the problem for a day and the problem came back next day.
Download the Hubitat app
