How to fix HomePod not showing in Now Playing app on watchOS 10?

I have an old Apple Watch 4 and it’s running the latest available software, a build of watchOS 10. Upon updating my HomePods to the new system 26, I realised I’m no longer able to access the HomePods in the Now Playing app. It doesn’t come up at all, neither does it launch the Now Playing app like it used to by default. I can change the volume only if the source is the phone (a phone running iOS 26), but not if the source is the HomePod itself. Can you help me fix this issue?

[Re-Titled by Moderator]