When using Laravel to handle WebAuthn authentication, developers could run into an unforeseen problem where the system needs a userHandle even if it is explicitly set to null. The "Invalid user handle" error, which frequently results from inconsistent encoding or poor credential management, may result from this. This problem can be fixed by knowing how Base64Url encoding operates and making sure that saved credentials match authentication requests. This article examines important fixes, such as properly managing multi-device authentication, handling user identities, and efficiently debugging authentication failures. Developers can guarantee a smooth and safe login process for their users by adhering to best practices.