I changed my wireless router and now cannot connect the home pods to it

They should join the network once the iOS device you used to set them up is on the network. If it doesn’t, you can manually change the Wi-Fi network that it's connected to. In the Home app on your iOS device, press and hold HomePod, tap Settings , then tap "Move HomePod to [your Wi-Fi network]."

Wait a few seconds, then ask Siri a question to see if HomePod is connected to Wi-Fi.

HomePod doesn’t support captive or subscription networks. If you set up HomePod to use one of these networks, you’ll need to reset HomePod and set it up again on a different Wi-Fi network.

If HomePod isn't responding - Apple Support