How get username from SAML2 IDP during login

I’m trying to collect the username of the user when they have been authorised through my IDP (SAML2) but I can’t get it. User login just fine but I want to collect the username to use New-PSUAuthorizationClaim

Anyone that know why? I have tried almost everything I can think of so far even this:

$Parameters = @{
    Type                     = "Saml2"
    CallbackPath             = "https://$($HostFQDN)/"
    MetadataAddress          = "xxx"
    EntityId                 = "https://$($HostFQDN)/sp"
    IdentityProviderEntityId = "xxx"
    SingleSignOnServiceUrl   = "xxx"
    ScriptBlock              = {
        New-PSUAuthenticationResult -Success
        if ($Null -ne $User.Identity.Name) {
            $UserName = ($User.Identity.Name)
            $UserName = $UserName.Split('\') | Select-Object -Last 1
        if ($Null -ne $Credential.UserName) {
            $UserOne = $Credential.UserName
        if ($Null -ne $User) {
            $UserTwo = $User
        $text = "Authentication success for Cred: $($UserOne) User: $($UserTwo) UserName: $($UserName)!"
        $text | Out-File "C:\Temp\adlogin.txt"
Set-PSUAuthenticationMethod @Parameters
Product: PowerShell Universal
Version: latest version 4