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Go to any Office app and ensure you’re signed in with the same Microsoft account linked to your license. Remove and re-add your account under the "Account" settings of the app if needed. If this doesn’t work, reset the credentials in your Windows Credential Manager Outlook OST vs PST repair or contact Microsoft support for further assistance. Despite its robust feature set and user-friendly design, it’s not uncommon for end users and IT professionals to encounter sign-in and activation issues. If you or your employees can’t sign in to Office 365, or if the applications repeatedly prompt for activation, productivity can grind to a halt. Yes, Microsoft 365 works offline for most apps like Word and Excel.
How do I fix the ‘Product Activation Failed’ error in Microsoft 365?
If you’re unable to sign in to your Microsoft 365 account, ensure you’re using the correct email and password. Locked accounts, due to multiple failed attempts, may require waiting or following unlock instructions. Check your internet connection, as weak connectivity can cause issues. For work or school accounts, confirm with your organization that your account is active. Browser or app issues, like outdated software or cached data, can also interfere; try clearing your cache or switching Outlook Stuck on Synchronizing Folders browsers. Troubleshooting Office 365 sign-in or activation issues can be straightforward if you approach the problem methodically.
Recover your account

If the issue persists, Microsoft has created a dedicated tool called Microsoft Support and Recovery Assistant (SaRA) to automate many troubleshooting tasks. The tool will ask you to enter the email address or mobile phone number you're trying to sign in with and check the details you provide. If we detect a problem with your account, we'll tell you what you need to do to solve the problem.
3 Step 3: Verify Network Connectivity and Firewall Settings
- Microsoft 365 is a vital tool for many businesses, and login issues can significantly disrupt day-to-day operations.
- If we detect a problem with your account, we'll tell you what you need to do to solve the problem.
- Close unused tabs, background processes, or applications to free up system resources.
- You have to follow a systematic approach while dealing with Microsoft 365 login issues.
- Perform a quick repair via "Programs and Features" to optimize performance.
Regardless of the root cause, understanding the core steps to troubleshoot and resolve these issues is essential for an efficient, well-run IT environment. A slow installation is often caused by network problems or background tasks monopolizing bandwidth. Close other programs or downloads running on your device to free up resources. If you’re still stuck, reboot your computer and try the installation again, preferably during off-peak internet hours. If network connectivity is solid and you’ve ruled out firewall or proxy blocks, clearing cached credentials and repairing the Office installation are the next logical steps. After running the tool, restart your system to clear any residual files.
Microsoft 365 Troubleshooting – Quick Fixes for Common Problems

Simply open the Office app normally, and all your files are saved locally until internet access resumes. For cloud-based services like Outlook or OneDrive, offline access won’t work until you sync online again. Make sure to save any updates for immediate syncing FixTechGuide mailbox repair steps once a connection is re-established.