Outlook Desktop - Repeated Sign-In Prompt (WAM BrokerPlugin Reset)

Document Type: Known Issue — Workaround
Applies To: Microsoft Outlook Desktop (Classic), Windows 10/11, Microsoft 365 / Exchange Online

Overview
This article documents a workaround for a recurring issue where Outlook Desktop prompts users to sign in repeatedly — as frequently as every 15 minutes to every hour — without retaining the session after completing authentication. This issue can affect individual users or a large number of users simultaneously across an organisation.

The Issue

Users open Outlook and are presented with a "Sign In" prompt unexpectedly. After signing in successfully, the prompt reappears again after a short period. The following self-service steps do not resolve the issue:

• Restarting the laptop or PC

• Signing out of Outlook and signing back in

• Restarting Microsoft Teams or other Office apps

The issue may also surface across other Microsoft 365 services (Teams, OneDrive, SharePoint) simultaneously, as they share the same underlying authentication component.