However, if the administrator is unable to resolve issues with the help of self-service support resources, they should Contact support. Technical support for Microsoft 365 operated by 21Vianet subscriptions provides assistance with basic installation, setup, and general technical usage. If you’re a volume licensing admin but are unable to access the admin center, you can create an online support request. With every subscription of Microsoft 365 operated by 21Vianet, 21Vianet support provides technical, presales, billing, and subscription support. Have your Microsoft 365 apps suddenly started crashing after a recent Windows or Office update? Many users experience random application freezes, launch errors, and constant crashes after installing new patches or cumulative updates.

⃣ Reset Browser Cookies Cache

If your admin enabled Modern Authentication (MFA), try disabling it temporarily via Azure Active Directory → Properties. Alternatively, generate an app-specific password if using Outlook 2016 or older. This resets your authentication cache and forces a fresh token request.

Microsoft 365 Apps Crashing After Update — Step-by-Step Repair Guide

• The steps to access the repair tool vary depending on your operating system.
• It automatically diagnoses and repairs many Office 365 problems — including search indexing and sync issues.
• This guarantees clean configuration files and resolves deep-level corruption issues.
• The Microsoft 365 Copilot app brings together your favorite FixTechGuide Office 365 support apps and Copilot in one intuitive platform.
• The Microsoft 365 Copilot app brings together your favorite apps in one intuitive platform that keeps your data secure with enterprise data protection.
• If your admin enabled Modern Authentication (MFA), try disabling it temporarily via Azure Active Directory → Properties.
• Microsoft 365 crashes after updates can be frustrating, but these fixes will restore stability quickly.
• For more self-help resources, see Microsoft 365 operated by 21Vianet.

For iPhone users, reinstalling Outlook or updating to the latest iOS often resolves stuck sign-in loops instantly. Many users have both personal Microsoft accounts (e.g., Exchange connectivity diagnostic Outlook.com) and work/school Office 365 accounts. If both are signed in simultaneously, the system can confuse the authentication path.

? Fix Office 365 Login Issues on Mobile

If all else fails, uninstall Microsoft 365 completely, remove remaining registry traces using the Office Uninstall Support Tool, and reinstall it fresh. This guarantees clean configuration files and resolves deep-level Outlook sync help from FixTechGuide corruption issues. Partial updates often break compatibility between Windows libraries and Office binaries.

Step 2 – Update Outlook and Office 365

Go to Settings → Windows Update and install all pending updates. Then open any Office app → File → Account → Update Options → Update Now to ensure both are synchronized. Go FixTechGuide Office 365 troubleshooting to Control Panel → Programs and Features, select Microsoft 365, and click Change → Quick Repair.





Microsoft 365 with Microsoft Teams helps deliver a complete, secure solution to help everyone work better, smarter, and more cohesively. Microsoft Create has professionally designed, fully customizable templates to help you get things done. Find solutions to common problems or get help from a support agent.