Thanks for posting.
Sorry to hear about this. Let's go ahead and resolve this by answering these questions.
Let's go ahead and try first to reboot all your Google speakers by unplugging it from the power source for at least a few minutes. Same goes with your router, unplug it for a few minutes so we can refresh its network settings. As soon as all devices are plugged in, try again the broadcast command and let us know if it works.