Microsoft 365 Customer Service and Support

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Download the tool from Microsoft and run the Outlook diagnostic to auto-detect server and account issues.



FixTechGuide support for Office 365

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



  • Have your Microsoft 365 apps suddenly started crashing after a recent Windows or Office update?
  • Go to Control Panel → Programs and Features, select Microsoft 365, and click Change → Quick Repair.
  • The administrator is expected to provide initial assistance for the customer’s users.
  • Alternatively, generate an app-specific password if using Outlook 2016 or older.
  • Incorrect system time can break your connection to Microsoft’s authentication servers.
  • This restores missing or corrupted Office components that affect search indexing.
  • 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.


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., Outlook profile repair and recovery steps 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 Outlook Not Sending or Receiving Email by 21Vianet portal to submit service requests online and access support telephone numbers.

FixTechGuide support for Office 365

Step 2 – Update Outlook and Office 365





We provide instant guidance for update errors, installation failures, FixTechGuide fix for stuck folders and Office activation issues. When Office 365 search stops working after updates, it’s usually a minor indexing or cache issue — not a major fault. Following the steps above should restore your search functionality quickly. For advanced troubleshooting, FixTechGuide offers remote support to restore performance and indexing accuracy for Outlook and other Office apps. Microsoft 365 crashes after updates can be frustrating, but these fixes will restore stability quickly.

FixTechGuide support for Office 365

Repair Outlook OST File Not Working in Office 365 – Complete Fix (



Outlook and Office 365 sync issues can be frustrating but are almost always fixable. Start with basic network checks, enable Cached Exchange Mode, and repair your data files if needed. 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 problem usually occurs due to authentication token mismatches, cached credentials, or browser session conflicts. In this guide, we’ll walk you through every step to fix Office 365 login problems on both Windows and the web version. If your Microsoft 365 suite keeps crashing or you can’t recover lost files, reach out for expert help right away.
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