Why am I seeing a "Pak is invalid" error when launching Fortnite?

We are aware that some players are seeing errors with "Pak is invalid" or "SignatureError". Our team is currently investigating the issue.

In the meantime you can try following these steps:

1. Verify game files by following the steps in How do I verify game files in the Epic Games Launcher?.
2. Delete the FortniteGame folder by following the steps in How do I remove the FortniteGame folder from %localappdata%?.
3. Reinstall Fortnite by following the steps in How do I reinstall Fortnite?.
4. Follow the guidelines in ESP Errors in Fortnite.