Powershell: Exception calling "Start" with "0" argument(s): Script1 invoking Script2

I have one script that is invoking another script. In order to get the output from the second script, I was told to use ProcessStartInfo and Process.

#script1.ps1

$abc = $args
$startInfo = $NULL
$process = $NULL
$standardOut = $NULL<#Previously created password file in C:\Script\cred.txt, read-host -assecurestring | convertfrom-securestring | out-file C:\Script\cred.txt#>
$password = get-content C:\Script\cred.txt | convertto-securestring
$startInfo = New-Object System.Diagnostics.ProcessStartInfo
$startInfo.FileName = "powershell.exe"
$startInfo.Arguments = "C:\script\script2.ps1", $abc
$startInfo.RedirectStandardOutput = $true
$startInfo.UseShellExecute = $false
$startInfo.CreateNoWindow = $false
$startInfo.Username = "DOMAIN\Username"
$startInfo.Password = $password 

$process = New-Object System.Diagnostics.Process
$process.StartInfo = $startInfo
$process.Start() | Out-Null
$standardOut = $process.StandardOutput.ReadToEnd()
$process.WaitForExit()
# $standardOut should contain the results of "C:\script\script2.ps1"
$standardOut

The code seems correct, but for some reason I am getting error that says my login is incorrect, even though I used $password in old code correctly

Exception calling "Start" with "0" argument(s): "Logon failure: unknown user name or bad password"
At C:\script\script1.ps1:46 char:15+ $process.Start <<<< () | Out-Null+ CategoryInfo          : NotSpecified: (:) [], MethodInvocationException+ FullyQualifiedErrorId : DotNetMethodException
You cannot call a method on a null-valued expression.
At C:\script\script1.ps1:47 char:49+ $standardOut = $process.StandardOutput.ReadToEnd <<<< ()+ CategoryInfo          : InvalidOperation: (ReadToEnd:String) [], RuntimeException+ FullyQualifiedErrorId : InvokeMethodOnNull
Exception calling "WaitForExit" with "0" argument(s): "No process is associated with this object."
At C:\script\script1.ps1:48 char:21+ $process.WaitForExit <<<< ()+ CategoryInfo          : NotSpecified: (:) [], MethodInvocationException+ FullyQualifiedErrorId : DotNetMethodException

If $password is correct, then why I am getting this error? How to troubleshoot?