First Harmony had a red skill. Then they had a red skill and a blue skill. Now they have discontinued the red skill and only have the blue skill.
https://support.myharmony.com/en-us/harmony-experience-with-amazon-alexa
At the same time, in the most recent Amazon update, they changed things somewhat so that Harmony activities will now automatically be added to the smart home section of your Alexa app as “scenes.”
But the smartthings/Harmony integration still creates virtual switches for each activity, which means you’ll see your Harmony activities twice with the same name in your Alexa app, once as a device controlled by smartthings and once as a scene controlled by Harmony.
Put all that together, and you may find that your Alexa/harmony interface works somewhat differently than it used to.
In particular, note that the language used has changed a little bit. If you have set up your channel numbers as favorites, you’ll still be able to say “Tell Harmony to switch to 5.” But if you didn’t set the channel up as a favorite, you now have to say “Alexa, go to channel number five“ which is different than it used to be.
Finally, if you have both a Fire TV and a Roku On the same television, you will probably have to say “Alexa, tell Harmony…” for quite a few things that are supposed to work without having to say “tell Harmony” because the echo clearly gets confused between the two devices.
It all takes some getting used to you if you were previously using the red skill. But it’s not anything is broken per se, it’s just that the red skill has been deprecated now.
Note that all of this is different than a separate issue where echo keeps telling you that it can’t do something when it actually can. And also Different from the separate issue where Alexa routines are not including the correct ST devices. Those two are actual bugs. The issue described in this post isn’t a bug, it’s a change in how the integration works. 
In my case, after talking to both logitech support and Amazon support and finally figuring out what the problem was, it turned out that the best way for me to fix it was to disable the blue skill, go through and mark all my channels as favorites, and then reenable the blue skill. Once I did that, everything worked the same way it used to as far as the words that we said.
We did find that we had to continue to say “tell Harmony” because of the issue of having both a fire TV and Roku on the same television, but since we had already been saying that it wasn’t a big deal for us.