While playing Spotify Premium on my Google Home speakers, I used to be able to say, "Hey Google, I like that" and magically that song would be added to my songs list in my Spotify library. This feature stopped working about 2 weeks ago. I have checked/rechecked my connection/authentication between Google and Spotify and everything is copacetic. Is this feature broken? For what it's worth, when I use the same feature when playing tracks on Google Play Music, it works perfectly.
Thanks for letting us know. The team is looking into the issue. In the meantime, I recommend that you try saying "I like this track" which I could confirm works. (You may also try "I like this album", "I like this artist", etc.)