HomePod

I have 4 HomePod. 3 full size, 1 mini. I used to be able to ask Siri to play music everywhere and it played the same music on all 4 devices. About a week ago I streamed a podcast from my iPad to all of the HomePods. Since then I have been unable to successfully ask Siri to play music to “everywhere “. She responds “now playing your station to everywhere “ but no music comes out. I can get individual HomePods to play but not all of them in sync. Any ideas?