Powershell Start-Process permission denied - powershell

Question

Could anyone tell me, why do I get an Error if I invoke:
$log = $env:TEMP + "\File.log"
$stdErrLog = $env:TEMP + "\stderr.log"
$stdOutLog = $env:TEMP + "\stdout.log"
$argument = "Get-Childitem c:\"
Start-Process powershell.exe -Credential $credentials -WindowStyle hidden -WorkingDirectory c:\ -ArgumentList $argument -RedirectStandardOutput $stdOutLog -RedirectStandardError $stdErrLog -wait
but there is no Error if I invoke:
Start-Process powershell.exe -Credential $credentials -WindowStyle hidden -WorkingDirectory c:\ -ArgumentList $argument -RedirectStandardOutput $stdOutLog -RedirectStandardError $stdErrLog
But I need the "-wait" or is there any alternative?
Error:
Start-Process : Permission denied
In Zeile:1 Zeichen:1
+ Start-Process powershell.exe -Credential $cred -WorkingDirectory c:\ -ArgumentLi ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [Start-Process], Win32Exception
+ FullyQualifiedErrorId : System.ComponentModel.Win32Exception,Microsoft.PowerShell.Commands.StartProcessCommand

Answer 1

Sounds like your current user doesn't have access to see processes running as the 2nd account. Launch a PowerShell window under the other account, then run the script below as yourself to see if it's visible. If not, you may need to elevate permissions or run as admin.
Get-Process powershell | select -ExpandProperty startinfo | select -expandproperty environmentvariables | ?{$_.Name -eq USERNAME}