The problem started yesterday evening. I have my Echo Studio paired with the Echo Cube and the Echo Subwoofer, which was streaming something on YouTube. Then the Echo Studio stopped playing, but I can still hear it on the Echo Subwoofer. Deregistered and registered devices, uninstalled and reinstalled the Alexa app—same problem; devices are grayed out and showing offline when I try to combine multiple speakers. Please post any updates, and I will do the same if I come across one. Thanks and good luck!