Can't launch the modded realm, but I can launch the official realm

Warhammer: Vermintide 2 Technical Support
3
  1. Press the Windows key + R
  2. Enter %appdata% and select the ‘OK’ button
  3. Navigate to AppData\Roaming\Fatshark\Vermintide 2
  4. Right-click user_settings.config and select ‘Properties’

Under ‘Attributes’, is the ‘Read-only’ checkbox selected? If so, deselect it and apply the changes.