I have two Pi4’s on my network that both show up in the Volumio app when I open it, and I can select either and they work great. I can directly navigate to the UI using the IP addresses or the local.volumio names. But when I click the Zones and Outputs icon in the playback screen, neither have the other device listed. I can also see both devices in the My Volumio menu and have Superstar subscription.
I did a fresh install on my bedroom Pi of V3 and did an update/factory reset on my den Pi. Both are connected wirelessly to the same router with only one subnet. I had one wired to my network switch and thought that was the issue but same with both on wireless only.
This was an issue with my two Pi4 devices running Volumio 2, but the new update got me motivated to get my bedroom streamer working again. I basically stopped using it because of this issue. Would like to get this working because it used to work great 6 or 9 months ago.