What makes outlook not to open but throw such kind of an error?

Mathye, Cyril 40 Reputation points
2026-09-01T07:34:04.0233333+00:00

What is causing the error below?

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Outlook | Windows | Classic Outlook for Windows | For business
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Helen Luu 2,785 Reputation points Independent Advisor
2026-09-01T10:12:18.97+00:00

Hello @Mathye, Cyril

I understand that you're experiencing an issue with Outlook Desktop, which is displaying the error message "Failed to fetch". This issue can occur for several reasons, including server-side problems, network connectivity issues, or an application-related problem.

To help troubleshoot the issue, could you please try the following steps?

  1. Changing the connection:
    • If you are using a VPN, proxy, antivirus, or firewall application, please try disabling it temporarily and then access Outlook again to see if the issue still occurs.
    • Try switching to a different network, such as another Wi-Fi connection or a personal hotspot, and check whether Outlook works properly.
  2. Repair the Outlook application:
    • Go to Windows Settings > Installed Apps (or Programs and Features) > select Microsoft Office or Outlook > choose Modify
    • Choose Quick Repair or Online Repair.
    • Follow the prompts and restart your device once the repair is completed.
  3. Clear the Outlook desktop cache:
    • Close Outlook completely.
    • Press Windows + R to open the Run dialog box.
    • Type %localappdata%\Microsoft\Outlook and press Enter.
    • Open the RoamCache folder then select all files (Ctrl + A) and delete them.

If the issue still persists, could you please let me know:

  1. Is your account using Exchange or is it managed by a third-party email provider? If it is an Exchange account, could you please check whether the issue also occurs in both New Outlook and Outlook classic?
  2. Are any of your colleagues experiencing the same issue? If yes, when did the issue start occurring?

I look forward to hearing from you.

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AI answer

2026-09-01T07:34:25.3666667+00:00

The error shown in the screenshot is not specifically explained in the available documentation, but the documented causes for Outlook failing to open or freezing include these common categories:

  1. Outlook is not fully updated.
  2. Outlook is being used by another process.
  3. An add-in is interfering with startup.
  4. Outlook data files are corrupted or damaged.
  5. The Outlook profile is corrupted.
  6. Another program is conflicting with Outlook.
  7. Antivirus software is outdated or conflicting with Outlook.
  8. Microsoft 365 program files need repair.

For classic Outlook for Windows, the supported first checks are:

  1. Run the classic Outlook startup troubleshooter.
    • Use the classic Outlook startup troubleshooter from Microsoft.
    • It must be run on the same Windows PC where classic Outlook is installed.
    • Windows 10 or later is required.
  2. Start Outlook in safe mode to test add-ins.
    • Press Windows key + R.
    • Type Outlook /safe and select OK.
    • If Outlook opens in safe mode, an add-in is the likely cause.
  3. Disable add-ins.
    • In Outlook, go to File > Options > Add-ins.
    • Ensure Manage shows COM Add-ins, then select Go.
    • Clear all selected add-ins and select OK.
    • Restart Outlook normally.
    • If Outlook opens, re-enable add-ins one at a time to find the one causing the error.
    • Do not remove add-ins during this test; disable them only.
  4. Create a new Outlook profile.
    • If Outlook does not start even in safe mode, create a new profile and test with it.
    • If Outlook starts with the new profile, the original profile is corrupted.
  5. Repair Outlook data files.
    • Use the Inbox Repair Tool (scanpst.exe) to scan and repair Outlook data files.

If the issue matches the Exchange-specific error “The attempt to log on to Microsoft Exchange has failed” and a Fiddler trace shows authentication concurrency limit is reached, that documented case requires opening a support case from the Microsoft 365 Admin portal. The documented workaround is to use Outlook Web Access (OWA) or new Outlook for Windows.

AI-generated content may be incorrect. Read our transparency notes for more information.

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