DLC items for V Rising may not appear as available in Offline LAN mode. This is a known issue the development team is currently investigating in order to resolve.
In order to enable your DLC items in Offline LAN mode, please restart the game while connected to the internet. This will allow the server to sync your available DLC. After starting the game in online mode at least once, the items should remain available in-game, even if you start in Offline LAN mode again later.