How to Fix Outlook Error ‘Something Went Wrong [1001]’

Quick Fix

Clear Outlook's cached sign-in data. Close Outlook completely, then on Windows go to C:\Users\%username%\AppData\Local\Microsoft\ and rename or move the IdentityCache and OneAuth folders elsewhere. Reopen Outlook so it prompts you to sign in fresh. On Mac, quit Office apps, open Keychain Access, search 'Office', and delete the related entries, then sign in again.

Step-by-Step Guide

What this error means

'Something went wrong [1001]' shows up when Microsoft 365 desktop or mobile apps (most commonly Outlook) fail during the sign-in/authentication process. According to Microsoft's own support documentation, the error "Something went wrong [1001]" is caused by security software impacting the WAM plug-in (AAD.BrokerPlugin) in one common scenario, and in a second scenario it's caused by user profile management issues, where on both VDI and physical devices roamed user profile data causes identity and authentication data components to be in a bad state. In short: something has corrupted or blocked the small local token/credential cache Outlook uses to verify your Microsoft 365 sign-in.

Cause 1: Corrupted local sign-in cache (most common on Windows)

1. Close Outlook completely. Make sure it isn't running in the background (check Task Manager).
2. Navigate to the identity cache folder. Open File Explorer and go to C:\Users\%username%\AppData\Local\Microsoft\. One IT support writeup confirms a temporary fix has been to go into the AppData\Local\Microsoft folder and cut the IdentityCache and OneAuth folders from the folder, paste them on your desktop and then open Outlook which will bring up the password prompt as if logging in for the first time.
3. Cut (not delete) the folders named IdentityCache and OneAuth and paste them temporarily onto your desktop as a backup.
4. Reopen Outlook. It should now show a fresh sign-in / password prompt instead of the error.
5. Sign in again with your Microsoft 365 account credentials.
6. Clean up. Once signed in successfully, you can delete the old backup folders from your desktop (do not paste them back over the new ones).

Cause 2: Security software blocking the WAM plug-in

1. Identify third-party security software (antivirus, endpoint protection, firewall tools) installed on the machine.
2. Temporarily disable or uninstall it to test — Microsoft's guidance notes that in order to expedite the investigation, uninstalling any security software completely and capturing MSOAID logs is recommended when submitting a support ticket.
3. Repair the broker plug-in via PowerShell. A Microsoft Q&A moderator suggests running these commands in user-mode PowerShell to repair WAM: reboot your computer and run the commandlets below in user mode PowerShell to repair WAM: Add-AppxPackage -Register "$env:windir\SystemApps\Microsoft.AAD.BrokerPlugin_cw5n1h2txyewy\Appxmanifest.xml" -DisableDevelopmentMode -ForceApplicationShutdown and Add-AppxPackage -Register "$env:windir\SystemApps\Microsoft.Windows.CloudExperienceHost_cw5n1h2txyewy\Appxmanifest.xml" -DisableDevelopmentMode -ForceApplicationShutdown.
4. Restart your computer after running the commands and try signing in to Outlook again.

Cause 3: Multi-Factor Authentication (MFA) misconfiguration (organization accounts)

1. Suspect this cause if the error keeps returning every few days even after clearing the cache. One IT consultant found this all points to Microsoft's enforcement of MFA pushed out sporadically since May 2023, as Outlook tries to re-authenticate but fails, and where MFA has been added but isn't enforced, it doesn't function correctly.
2. Ask your Microsoft 365 admin to check MFA status. The confirmed fix: the M365 Administrator needs to go into the Microsoft 365 Admin console and change the user from disabled to Enable within the Multifactor Authentication settings dashboard.
3. Remove the email account from Windows Accounts. After MFA is properly enabled, go to Settings > Accounts > Email & Accounts and remove the affected account.
4. Re-add the account, ideally after first signing in at https://outlook.office.com and completing authentication setup with the Microsoft Authenticator app, then re-add credentials in the Outlook desktop client.

Cause 4: Windows Work/School account conflicts

1. Open Windows search and type Accounts, then open Access work or school settings.
2. Disconnect the affected Microsoft account(s) listed there — a user-verified fix confirms removing accounts in Windows through the Work or School accounts section resolved the 1001 error.
3. Wait for it to disconnect, then relaunch Outlook and sign back in with your password when prompted.

Cause 5: Mac-specific fix

1. Quit all Office apps completely.
2. Open Keychain Access. Go to Finder > Applications > Utilities > Keychain Access, as confirmed in Microsoft Q&A guidance: quit all Office apps, go to Finder > Applications > Utilities > Keychain Access, and remove the identities related to Microsoft Office — search for 'Office' and delete everything.
3. Reopen Outlook and sign in again from scratch.

Cause 6: Mobile app (iOS/Android) sign-in error

1. Check your internet connection is stable before retrying.
2. Update the Outlook app to the latest version from the App Store or Google Play.
3. Clear the app's cache and data in your phone's app settings.
4. Try installing and signing into OneDrive first. One Microsoft Q&A answer found success this way: they had the client uninstall the apps, then install the OneDrive app first, and once OneDrive was authenticated, all other apps authenticated after that.
5. If it still fails, uninstall the Outlook app entirely, restart the phone, and reinstall fresh.

Fallback: Repair or reinstall Office

1. Run a repair. Go to Settings > Apps, find Microsoft Office or Microsoft 365, choose Modify, then pick Quick Repair first, and Online Repair if that doesn't work.
2. Scan for malware if the issue appeared unexpectedly, since infections can also trigger this error.
3. Reinstall Office completely as a last resort via Control Panel > Programs and Features > Uninstall, restart, then reinstall.

When to escalate

1. Contact your IT admin if you're on a work/school account — this is very often an MFA or Conditional Access policy issue only an admin can fix from the Microsoft 365 Admin Center.
2. Open a Microsoft support ticket if none of the above works. Microsoft states if you see this issue, ask your tenant admin to open a support ticket in the M365 Admin Portal, including MSOAID authentication logs.
3. Use Outlook Web Access as a workaround in the meantime — Microsoft notes you can work around this issue by using Outlook Web Access (OWA), Office Web Applications, or mobile applications while the desktop issue is resolved.