error: Assertion:AccountSourceListStore is not initialized in the new Outlook

Question

error: Assertion:AccountSourceListStore is not initialized in the new Outlook

So this was the first time i tried the new outlook and now outlook does not start, with error message

Header 1	Header 2
Cell 1	Cell 2
Cell 3	Cell 4

Answer 1

Hi @Stefan Burm, 

Thank you for posting your question in the Microsoft Q&A forum. 

Based on the details you shared, New Outlook started for the first time and now will not open because it stops with the message “Assertion:AccountSourceListStore is not initialized.” I genuinely recognize the time you have spent testing the new experience and sharing the exact error, and I appreciate the effort you have taken to help us pinpoint the cause. 

This can happen when the first run setup is interrupted or does not complete successfully, which prevents the account source store from being created correctly. In addition, New Outlook depends on locally stored app data and components used to load sign in and account information, so if that local state becomes inconsistent, the app may fail during startup. As a result, Outlook cannot finish initializing the account list and it closes with the assertion error. 

Since you haven’t specified your account type, I may not be able to provide an exact solution. However, assuming you're using a work account, you may consider the following steps that suit for your situation:   

1/ Repair and reset New Outlook app data 

• Close New Outlook completely. 
• Open Windows Settings, then select Apps, then select Installed apps. 
• Locate Outlook (new) or Microsoft Outlook, then open Advanced options. 
• Select Terminate, then select Repair. 
• If the issue continues, return to the same page and select Reset. 
• Reopen New Outlook and complete the sign in prompts. 

2/ Rebuild the local cache by renaming the LocalState folder 

• Close New Outlook, then open Task Manager and confirm Outlook is not running. 
• Press Windows key + R, enter the path below, then select OK. 

%LocalAppData%\Packages\ 

• Find the folder that begins with Microsoft.OutlookForWindows. 
• Open the folder, then rename LocalState to LocalState.old. 
• Start New Outlook again so it can recreate the required store automatically. 

3/ Repair Microsoft Edge WebView2 Runtime 

• Open Windows Settings, then select Apps, then select Installed apps. 
• Locate Microsoft Edge WebView2 Runtime, then select Modify. 
• Choose Repair, then restart your device. 
• Launch New Outlook again and check whether it opens normally. 

4/ Reinstall New Outlook to refresh the installation state 

• Open Windows Settings, then select Apps, then select Installed apps. 
• Select Outlook (new), then select Uninstall. 
• Restart your device to clear remaining background components. 
• Install Outlook (new) again from the Microsoft Store, then open it and sign in. 

5/ Contact IT administrator: 

Since your account is managed by your organization, please contact your IT administrator to review your permissions and policies. If the issue persists after these checks, ask your IT administrator to submit a support request directly to Microsoft Support team.      

They can raise a support ticket by visiting: Get support - Microsoft 365 admin | Microsoft Learn 

If the error remains after completing the steps above, please reply with your Windows version, and a screenshot of the full error window. With those details, I can provide the most targeted next action for your environment. 

As community moderators, we appreciate your understanding that our access to internal development details is limited. Our primary role is to guide users toward the appropriate resources and support channels. While we may not have visibility into deeper backend analysis, we’ll continue doing our best to support you within the scope of our responsibilities.    

I hope this information is helpful. Please follow these steps and let me know if it works for you. If you have any updates regarding the issue, please feel free to share them with me.      

Thank you for your patience and your understanding. I look forward to continuing the conversation.

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".      

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.  

Answer 2

The error message you are encountering, "Assertion: AccountSourceListStore is not initialized in the new Outlook," suggests that there may be an issue with the configuration or initialization of the new Outlook application. Here are some steps you can take to troubleshoot this issue:

1. Delete Specific Folders: Close all Microsoft applications, including Outlook. Then, navigate to the following directories and delete the folders:
   • C:\Users\(User Name)\AppData\Local\Microsoft\Olk
   • C:\Users\(User Name)\AppData\Local\Microsoft\OneAuth This action will remove any corrupted settings that might be causing the issue. These folders will be recreated automatically when you reopen the apps.
2. Repair Outlook: If the issue persists, consider performing an online repair of Outlook. This can help fix any underlying issues with the installation.
3. Check Compatibility Settings: Ensure that Outlook is not running in compatibility mode. You can do this by right-clicking on Outlook.exe, selecting Properties, and checking the Compatibility tab to ensure that the compatibility mode option is unchecked.
4. Reinstall Outlook: As a last resort, if none of the above steps work, you may want to uninstall and then reinstall the new Outlook application to ensure a clean installation.

If you continue to experience issues, it may be helpful to check for any updates or patches for the new Outlook that could address this specific error.

---

References:

• Outlook is unable to start in Windows 7 or 8
• You cannot start Outlook in cached mode or create a new cached mode profile