If the issue persists, repeat the process and choose Online Repair. This process replaces damaged core files without removing your data or customizations. 21Vianet also expect customer to collaborate at reasonable level accordingly.

⃣ Reset Browser Cookies & Cache

Support is available both online through the Microsoft 365 operated by 21Vianet portal, and by telephone for both paid and trial subscriptions. The Microsoft 365 Copilot app brings together your favorite apps in one intuitive platform that keeps your data secure with enterprise data protection. With Microsoft 365, you can designate several types of administrators who serve different functions. This service description uses the generic title administrator to refer to all categories of administrators.

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

• Go to Control Panel → Programs and Features, select Microsoft 365, and click Change → Quick Repair.
• Whether it’s Outlook, Word, or Excel, these fixes ensure your data is re-indexed, searchable, and synced properly.
• Alternatively, generate an app-specific password if using Outlook 2016 or older.
• Incorrect system time can break your connection to Microsoft’s authentication servers.
• We’ll walk you through step-by-step solutions for Office, Outlook, or Teams sign-in errors.
• Explore learning tools to collaborate on projects together and independently, all in one place.

Assistance for billing and subscription management issues is available online or by telephone during China business hours (Beijing Time), Monday through Friday. Billing and subscription management support can be accessed using the same phone number and online service request process as with technical support. The support telephone number can be found on the Outlook Stuck on Synchronizing Folders Microsoft 365 operated by 21Vianet portal. 2 Severity A is only available to customers who signed an advanced online service agreement with 21Vianet through a sales account manager. Download and run the official Microsoft Support and Recovery Assistant (SaRA).

? 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 OST vs PST repair 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 Office 365 Sync Errors Fix 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.