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

21Vianet understands that receiving timely technical support from qualified professionals is a key aspect of cloud services. Equally important is the critical role that the customer’s IT department plays in the support of its users. The Microsoft 365 operated by 21Vianet technical support team troubleshoots only those issues that are related to Microsoft 365 operated by 21Vianet. Incorrect system time can break your connection to Microsoft’s authentication servers. Always enable Set time automatically and select the correct region in your Windows settings.

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

• If all else fails, uninstall Microsoft 365 completely, remove remaining registry traces using the Office Uninstall Support Tool, and reinstall it fresh.
• Start with basic network checks, enable Cached Exchange Mode, and repair your data files if needed.
• For iPhone users, reinstalling Outlook or updating to the latest iOS often resolves stuck sign-in loops instantly.
• For persistent problems, rebuild your Outlook profile or use FixTechGuide’s free diagnostic tools to automate detection of authentication and IMAP errors in seconds.
• The support telephone number can be found on the Microsoft 365 operated by 21Vianet portal.
• In this guide, you’ll learn how to fix Office 365 search not working after update using step-by-step methods verified to restore indexing and search functionality.

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., Fix Outlook and Office 365 Errors 2025 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

21Vianet assigns a severity level to a case when it’s opened, based on an assessment of the issue type and customer impact. Examples of issue types and severity levels are shown in the following table. Authorized administrators can use the Microsoft 365 operated repair PST file without data loss by 21Vianet portal to submit service requests online and access support telephone numbers.

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 modern authentication troubleshooting to Control Panel → Programs and Features, select Microsoft 365, and click Change → Quick Repair.





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