We’ll need a little more information to take action on this report. Does this occur with every Zone, including the System Output (if available) of your RoonServer machine?
I assume you’re referring to the Tracks browser within Roon here, and not another page?
Do the tracks successfully populate in the Queue? You should see a track populate the Playback bar for the selected Zone.
When playback fails to initiate, does Roon present any error message?
The team has activated diagnostics for your RoonServer and will check if logging contains any more precise indications of the issue in the meantime.