Using Invoke-PolicyEvaluation with SQL Server authentication

On the web I can't find much about invoking policy evaluation via the PowerShell Cmdlet Invoke-PolicyEvaluation with SQL Server authentication.

Something like this worked in the past, but after upgrading to SQL Server 2016 it won't work. It works with Windows authentication.

$conn = New-Object Microsoft.SqlServer.Management.Sdk.Sfc.SqlStoreConnection("Server=$ServerName;Integrated Security=False;User=PolicyEvaluation;Password=...")                
 Get-ChildItem | Where-Object {$_.Name -eq $Policy.Name} | Invoke-PolicyEvaluation -TargetServerName $conn -AdHocPolicyEvaluationMode $EvalMode -OutputXML > $OutputFile

I get this error:

Get-ChildItem : SQL Server PowerShell provider error: Failed to read child items. [The pipeline has been stopped.]
At D:\EnterprisePolicyManagement\PowerShell\EPM_EnterpriseEvaluation_412.ps1:278 char:6
+                     Get-ChildItem | Where-Object {$_.Name -eq $Policy.Name} | Invoke-PolicyEval ...
+                     ~~~~~~~~~~~~~
    + CategoryInfo          : ReadError: (SQLSERVER:\SQLP...EFAULT\Policies:SqlPath) [Get-ChildItem], GenericProviderException
    + FullyQualifiedErrorId : CannotReadChildItems,Microsoft.PowerShell.Commands.GetChildItemCommand