HomePod unable to join Wi-Fi network

I have a couple of the large HomePods, and both have been working fine for months. Recently they couldn't connect to the WiFi network though, so I reset both of them, and now whenever I try to connect them to the network, I get a message on my iPhone (iOS 15.1.1) saying:

HomePod could not connect to the Wi-Fi network "?".

My network name isn't "?", and my iPhone is connected fine to the WiFi network. All my other devices connect just fine as well. I even tried turning off the "Private Address" setting for that network on my iPhone, but that didn't seem to help. Anyone have any other ideas?