I had this same issue and opened a support case with tp-link. After a few back and forths, I found my issue. When I enabled the skill in the Alexa app, I used a different account than the one that...

I have the same issue with plugs and switches (work in Kasa app but not Alexa). The process described in this post for fixing sounds logical, but is a giant pain in the you-know-what when you have 15...