HomePod can't play "everywhere"

I have four HomePods. If something was playing on just one I used to be able to say "Hey Siri, play this everywhere" and the song would start playing all over the house. Since the last update (I'm running 15.5.1) this no longer works. If I say "Hey Siri, play this everywhere," she now responds, "Sorry, I can't find (name of the song currently playing) in your Apple library." Anyone else having this problem, or have a solution? Needless to say, I've reset all of my HomePods multiple times, but it doesn't fix this problem.

It seems like every update just creates new problems. It's frustrating -- I love my HomePods and use them every day, but they have NEVER worked entirely correctly since the day they were released. It's amazing to me how buggy this software STILL is, at version 15!