Get-PowerBIWorkspace returned "Login first with Login-PowerBIServiceAccount"

"Get-PowerBIWorkspace" works on local. But doesn't work from EasyMorph server powershell. A few days ago, it was working, but recently it gives following error.

Login first with Login-PowerBIServiceAccount
I have already logged with "Login-PowerBIServiceAccount".

My code is:

Login-PowerBIServiceAccount -Credential $MyCredential

$workspaces = Get-PowerBIWorkspace -scope Organization
$workspaces.count

Powershell version:
5.1.14409.1018

MicrosoftPowerBIMgmt version:
1.0.726

"Resolve-PowerBIError -Last" result:

Message        : Login first with Login-PowerBIServiceAccount
StackTrace     :    at Microsoft.PowerBI.Commands.Common.PowerBICmdlet.AssertProfileExists()
                    at Microsoft.PowerBI.Commands.Common.PowerBICmdlet.BeginProcessing()
                    at Microsoft.PowerBI.Commands.Workspaces.GetPowerBIWorkspace.BeginProcessing()
                    at System.Management.Automation.Cmdlet.DoBeginProcessing()
                    at System.Management.Automation.CommandProcessorBase.DoBegin()
Exception      : System.Exception
InvocationInfo : {Get-PowerBIWorkspace}
Line           : $workspaces = Get-PowerBIWorkspace -scope Organization
                 
Position       : At line:38 char:15
                 + ... orkspaces = Get-PowerBIWorkspace -scope Organization |  ...
                 +                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
HistoryId      : 1

Start by reproducing the sequence using Login-PowerBIServiceAccount and Get-PowerBIWorkspace -Scope Organization in PowerShell 5.1 with MicrosoftPowerBIMgmt 1.0.726, then inspect the Resolve-PowerBIError -Last output and the reported AssertProfileExists entry point. Done means explaining or correcting why the authenticated profile is not recognized in the EasyMorph server environment while it works locally.