The error "Sequence contains more than one matching element" typically points to a server-side issueโmost likely a duplicate record in a database or identity provider mismatch where the system expects a single unique user entry but finds multiple.
Hereโs a breakdown of whatโs likely going on and steps to resolve it:
What It Means
The login process is querying a user record (by email, username, or some other key).
It expects exactly one match.
It found multiple matches.
This causes the system to throw an exception instead of handling the ambiguity.
Common Causes
1. Duplicate entries in the user database (same email/ID appearing more than once).
2. Misconfigured Identity Provider (IdP) integration (e.g., Azure AD, Google Workspace) returning multiple identity claims.
3. Database constraint or sync issues, possibly caused by recent changes in your auth/user setup.
4. Caching issue where stale user data is conflicting with updated identity data.
What You Can Do
If you have backend or admin access:
Check the user table (wherever itโs storedโSQL, Azure AD, etc.) for duplicates.
Search by the email address or user identifier of the person trying to log in.
Remove or merge duplicates if found.
If you're using Azure AD / SSO:
Go into Azure Portal > Azure Active Directory > Users.
Check for users with the same email but different object IDs.
Also look at "Enterprise Applications" > [Your App] > Users and Groups.
If youโre the app admin but not backend admin:
Report the issue to your IT team or the app developer.
Provide a screenshot and the email of an affected user.
Mention that duplicate records are likely the issue.
Short-Term Fix
If you can identify a user with the issue, try:
Deactivating one of their duplicate records (if possible).
Clearing any cached tokens/sessions from the identity provider.
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