Outlook won't sign in and shows "Something went wrong" with error tag 657rx. This happens when cached Azure AD or work/school account credentials get corrupted or conflict with each other.
The Fix
Open Settings and disconnect any stale work or school accounts:
Settings > Accounts > Access work or school
Look for any accounts listed and click Disconnect on each one.
Then clear the cached identity folders. Close all Office apps first:
# Close all Office apps, then run:
Remove-Item "$env:LOCALAPPDATA\Microsoft\OneAuth" -Recurse -Force -ErrorAction SilentlyContinue
Remove-Item "$env:LOCALAPPDATA\Microsoft\IdentityCache" -Recurse -Force -ErrorAction SilentlyContinue
Restart your PC and relaunch Outlook. Sign in fresh when prompted.
Verify
Outlook should launch and prompt for credentials. After signing in, the error shouldn't return.
If it persists, run an Online Repair:
Control Panel > Programs > Programs and Features > Microsoft 365 > Change > Online Repair
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