Windows Error 691 — Authentication Failed

Windows network error 691 means the remote connection was denied because the username and password combination was not recognized. This guide covers everything you need to know about this topic, including common causes, step-by-step solutions, and answers to frequently asked questions.

Here are the key things to understand: Error 691 — access denied during network authentication. Username or password rejected by the server. Common with VPN and dial-up connections. ISP may have changed credentials. Understanding these fundamentals will help you diagnose and resolve this issue more effectively.

The most common reasons this occurs include: Incorrect username or password entered. ISP changed authentication credentials. Caps Lock is on when entering password. Account expired or suspended by ISP. Identifying the root cause is the first step toward finding the right solution.

To resolve this, follow these recommended steps: Double-check username and password — watch for Caps Lock. Contact ISP to verify correct credentials. Delete saved credentials and re-enter. Check if ISP account is active and not suspended. If these steps do not resolve the issue, consider consulting additional resources or a qualified professional.

This article is part of our Windows Error Codes collection on Error Codes Wiki. We provide comprehensive, up-to-date information to help you find solutions quickly.