Office 365 Won't Sign In: Understanding Session Lifetimes and Authentication Tokens

Microsoft's Office 365 suite relies heavily on Azure Active Directory (Azure AD) to authenticate and authorize user access to various resources. This authentication process involves the use of both access tokens and refresh tokens, which have specific lifetimes that can impact your ability to sign in to Office 365.

Access Tokens: A Quick Overview

An access token is a JSON Web Token (JWT) provided after a successful authentication. It's valid for only one hour, meaning you'll need to re-authenticate periodically to maintain access to Microsoft 365 resources. This process is known as modern authentication.

Refresh Tokens: The Longer-Lived Alternative

In addition to access tokens, Office clients also use refresh tokens to obtain new access tokens when the existing ones expire. Refresh tokens are valid for a longer period, typically until revoked. When you use your credentials to sign in to Office 365, an exchange occurs between your client and Azure AD. This exchange succeeds if your initial authentication is still valid.

Session Lifetimes: Understanding the Timing

Microsoft 365 services have different session timeouts to accommodate their typical use cases. For example:

* SharePoint Online: If you access the service after more than 24 hours of inactivity, the timeout value is reset to five days.

* Admin Center: You'll be asked to provide credentials every eight hours if you choose not to keep yourself signed in for an extended period.

The following table outlines the session lifetimes for various Microsoft 365 services:

| Service | Session Lifetime |

| --- | --- |

| SharePoint Online | Up to 5 days after 24+ hours of inactivity |

| Admin Center | Every 8 hours or until you choose Keep me signed in |

| Microsoft Teams | Varies, but generally lasts as long as your access token |

When a session expires, users are prompted to re-authenticate. This can happen due to various reasons such as:

* Inactivity: When users haven't interacted with the service for an extended period.

* Browser or tab closure: Sessions can expire when users close their browser or tab.

* Authentication token expiration: This can occur due to password reset, token revocation, or other security-related issues.

In summary, Office 365 won't sign in if your authentication tokens have expired. By understanding the lifetimes of access and refresh tokens, as well as the session timeouts for various Microsoft 365 services, you can better manage your credentials and avoid unnecessary prompts for re-authentication.

Office 365 won39t sign in