Get-RdsDiagnosticActivities returns no activities, even when setting tenant name and upn

Recently, we have noticed that the get-rdsdiagnosticactivities command returns no results.  It completes (doesn't error out), but simply returns empty.

PS C:\temp> Get-RdsDiagnosticActivities -TenantName dclwvd
Get-RdsDiagnosticActivities : There were no activities found.
At line:1 char:1
+ Get-RdsDiagnosticActivities -TenantName dclwvd
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : FromStdErr: (Microsoft.RDInf...osticActivities:GetRdsDiagnosticActivities) [Get-RdsDiagnosticActivities], RdsPowerS
hellException
+ FullyQualifiedErrorId : ActivitiesNotFound,Microsoft.RDInfra.RDPowershell.Diagnostics.GetRdsDiagnosticActivities

This happens across multiple users/appids, clients, tenants, and subscriptions, when permissions are fully set via RDS Owner role.

Is there a service issue, or what am I missing?