AD - The server has rejected the client credentials

Get-ADGroupMember : The server has rejected the client credentials.
+ $gruppen | %{$all += Get-ADGroupMember  $_ -Recursive -Server $Server -Credentia ...
+                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : SecurityError: (Internet:ADGroup) [Get-ADGroupMember], AuthenticationException
    + FullyQualifiedErrorId : ActiveDirectoryCmdlet:System.Security.Authentication.AuthenticationException,Microsoft.ActiveDirectory.Management.Commands.GetADGroupMember

$all = @() 
$gruppen = @("Internet")   
$text = @()
$Utf8NoBomEncoding = New-Object System.Text.UTF8Encoding($False)
$gruppen | %{$all += Get-ADGroupMember  $_ -Recursive -Server $Server -Credential $cred }
$gruppen | %{$all += Get-ADGroupMember $_ -Server $Server -Credential $cred | ?{$_.objectClass -eq "group"} | Get-ADGroupMember -Recursive  }