I think you really need a bit more detail to get an answer.
- How did you create the wifi mesh network?
- How did the devices on the wifi mesh network access a router or did they ever need to route outside your condo?
- What type of devices are using the wifi mesh network besides speakers?
- How is the device with 'Johnwifimesh' connected to your network? What device is it? What firmware is it running?
What I think you really have is simple wifi network and for whatever reason, the new Xfinity device is not able to reach all of your remote devices. My limited understanding of mesh networks (Z-wave) is that all but a few devices are capable of routing traffic on the mesh so if you truly have a wifi mesh network I would think that means all devices that can reach the new Xfinity device on 'Johnwifi' are not also routing devices, the mesh network is non-existent, but those devices would still 'work'. I think that your 'old' device that is now using ESSID 'Johnwifimesh' is a router/wifi device right? If so, you *could* turn it into a wireless Access Point (AP) but that generally requires running some 3rd party firmware and you would need to cable it back to the Xfinity device. You would change its ESSID to be 'Johnwifi' and your devices would start working.
Maybe I'm jumping the gun here. Maybe your 'other' devices have bound to the radio of your old device and you need to tell them about the new Xfinity device. Again, more detail would really help in figuring out what the problem is and how to solve it.
