Homepod's Siri not responding

Hello,

My partner and I have a HomePod in our home office and have been using it for over a year now. However, two weeks or so ago, Siri stopped responding to my partner's commands. It works perfectly for me. The Homepod is linked to my apple account, but he has admin rights in the Home app.

I have already reset the HomePod two times, and, one time, it worked again for his voice, but after a few minutes, it stopped working again.

We have a family Apple Music account. Do you think this issue has something to do with the new subscription?

I don't know if it's related, but I have upgraded his iPhone to the latest iOS and enabled "Hey, Siri" on his phone, even though he has never used Siri on his phone, and it never caused an issue with the HomePod before.