Microsoft 365 Customer Service and Support

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The Microsoft 365 Copilot app brings together your favorite apps in one intuitive platform that keeps your data secure with enterprise data protection.



FixTechGuide support for Office 365

We can help you find a solution or connect you to technical support. This restores missing or corrupted Office components that affect search indexing. If a Microsoft 365 application such as Word or Excel isn't working correctly, sometimes restarting it will fix the problem. Download the tool from Microsoft and run the Outlook diagnostic to auto-detect server and account issues.

⃣ 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



  • With Microsoft 365, you can designate several types of administrators who serve different functions.
  • If your Microsoft 365 suite keeps crashing or you can’t recover lost files, reach out for expert help right away.
  • If your country/region isn’t listed, select a neighboring country/region or dial the United States support phone number.
  • This process replaces damaged core files without removing your data or customizations.
  • Partial updates often break compatibility between Windows libraries and Office binaries.
  • You must have at least one subscription bought through Microsoft to access Microsoft support.
  • Microsoft 365 Basic now comes with 100GB of cloud storage, secure photo and file storage, secure ad-free email, and technical support.


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 repair corrupted OST in Outlook 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



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 connection status shows disconnected 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



FixTechGuide support for Office 365

This ensures that the system-wide search index service is active and linked to Office 365 apps. Then, navigate to File → Options → Add-ins, and disable all non-Microsoft add-ins. If your country/region isn’t listed, select a neighboring country/region or dial the United States support phone number. For a smoother support experience, we recommend that you open separate support requests for each issue. You must have at least one subscription bought through Office 365 sync problems and login fixes Microsoft to access Microsoft support. The steps to access the repair tool vary depending on your operating system.

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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