AAD Discovery workflow error: "CDS.Library.AbandonedException: Could not find any available CDS PowerShell users" (4331969)

We setup and ran the Active Directory Environment Discovery task twice with the same results. What is causing this error?

"CDS.Library.AbandonedException: Could not find any available CDS PowerShell users in elapsed:00:10:03.9507505
   at CDS.AzureLibrary.CDSPowerShellPool.GetPowerShell(Boolean useTeams, Boolean useAzureAd, Boolean importExchange)
   at CDS.AzureLibrary.AzureAD.<GetChangedIds>d__36.MoveNext()
   at CDS.Model.Office365.<GetDeltaObjectsByType>d__72.MoveNext()
   at CDS.Model.Office365.<GetDeltaObjects>d__68.MoveNext()
   at CDS.Model.PushJob.Run(IWebServiceFactory webServiceFactory, CancellationToken cancellationToken)
   at CDS.Model.Job.Execute(IWebServiceFactory webServiceFactory, CancellationToken cancellationToken)
   at CDS.Model.Agent.ExecuteJobs(CancellationToken cancellationToken)
   at System.Threading.Tasks.Task`1.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()"