Run an update for your Sonos and controller, check the Settings to make sure all are on the latest version.

Power down all Sonos, reboot router and controller, power up Sonos.

If the problem persists submit a diagnostic and call Sonos support with the number it gives you.

Moderator edit: Sonos ID removed

That matches what I have here.

How about your speakers versions?

Settings - Manage - About your system

Down a bit you’ll have a Speaker type  :Room name

Under that you’ll have a Version like 82.2-59204

App: https://support.sonos.com/en-us/article/release-notes-sonos-app-updates

System: https://support.sonos.com/en-us/article/release-notes-sonos-system-updates

Best not to post screenshots of system specific information, the mods are tasked with removing that and they don’t need the extra work. :-)

All of my speakers have the latest firmware, so that is not the issue. This seems to have been some sort of transient bug. I cleared the app cache and restarted it on my Android phone, but that did not seem to help. The same issue occurred when I started the app after the cache clear, but then after it had been running in the background for a few minutes, things started working. The currently playing song appeared in the app as well as the volume slider. So, seems like a refresh/startup issue in the app? I do have 17 speakers, so maybe related to that? I should also mention that all of the speakers are Play 1’s and are all set up as stereo pairs, with only one being set up solo (a newer Sonos One), and with 2 of the pairs linked to soundbars (one Beam Gen2 and one original Playbar) Still, it does not instill a lot of confidence in me that the app has been well designed or debugged, especially under load or in a high speaker count situation. Sigh...

I have found the Android App menu’s “Force Stop” useful to get the Sonos App to behave.

Slightly faster to remember, find and use than rebooting the Controller’s device.