When you click on Authorize. is there any error message pop up?
Are you able to control the HS100 remotely via the kasa app?
Better to turn on the remote control, then turn it back on on the kasa app to check the function of the remote control

I had the same problem. In the end I found I had to exit the Kasa app on all devices first and then Google Assistant would authorise correctly.

Looks like I'm having same or similar problem. I have 2 switches (HS200 v2) fully working within kasa app (remote is enabled). But I can't get google home (assistant) to link kasa. As soon as I enter my kasa account info, I get this message "something went wrong. Try again". I have tried with kasa opened, closed, making sure it is not opened on other phone/ipad. I've been trying it for the past 2 days. Is there an issue with google/kasa or I'm missing something basic here. I have a google home mini working correctly.

I created an account with Alexa to test linking with Kasa and everything seems to have worked there.

This is driving me nuts.

Thanks

Do you guys have both Google Home and Google Assistant installed? If so, uninstall the Google Assistant. Try again.