Windows – Why is the logon script not mapping any drives

I've written a logon script in PowerShell. The Script is embedded in GPO and runs when a user is logging into the domain.

My Problem is, that the drives I deploy in the Script don't get deployed. I'm sure the logon script runs because in the end of the script i send an email to myself and I always receive it. So running the script should not be the problem. I'm also logging the whole $Error Variable each time the script runs and there is no indication to why this error occurs.

I'm almost certain that the error is not in the script itself – it has to be a permission error i think.

I think that this could be solved when I specify the -NoProfile Parameter when running the script, but I don't know where to put this in the GPO. I don't want a batch file calling the script because of beauty reasons :-).

Edit: specifying -noprofile didn't solve the issue

Edit: Since there was a comment saying there is not enough information about how the drives are mapped, I pasted the whole mapping part below:

# UserOU as a parameter, value set in GPO
Param([string]$UserOU)

# preparing some stuff...
Import-Module .\SecureStringFunctions.psm1
[Byte[]]$key = (1..16)
$pw = Get-Content .\LocalAdminCred.txt | ConvertTo-SecureString -key $key

# Tried this to elevate the Script IF it's needed. Didn't solve my problem. works only on PS 4.0 but didn't solve the issue on my 5.0 machine
if (!([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole] "Administrator")) 
{ Start-Process powershell.exe "-NoProfile -ExecutionPolicy Bypass -File `"$PSCommandPath`"" -Verb RunAs; exit }

# Import CSV with drive information based on username and userOU to get every maps that the current user needs
# also replacing a string inside the CSV for current session to map the homedrive of each user
$Drives = (Get-Content .\NetworkDrives.csv) -replace "userhome",$env:username | ConvertFrom-CSV -Delimiter ';' | ? {
    (($_.Group.split(',') -contains $UserOU) -or ($_.Group.split(',') -contains $env:username)) -and (!(Test-Path $_.Letter))
} 

# When I export the $Drives Variable at this point, all drives were read correctly, so the failure must occur in the mapping

# map all drives for current user. Drives to DMZ with password in plain text because ".mapnetworkdrive" only accepts plain text.
$Drives | % {
    if (![system.string]::IsNullOrEmpty($_.Username)) {
        if (($UserOU -like 'admin*') -and (($_.Server -ne $env:computername) -or ([system.string]::IsNullOrEmpty($_.Server)))) { 
            Continue
        }
        [string]$pwplain = ConvertFrom-SecureString $pw -AsPlainText -Force
        $Map = New-Object -comobject Wscript.Network
        $Map.MapNetworkDrive($_.letter,$_.path,$false,$_.username,$pwplain)
        $pwplain = ""
    } else { 
        $Map = New-Object -comobject Wscript.Network
        $Map.MapNetworkDrive($_.letter,$_.path,$false)    
    }
}