Azure AD B2C custom policy Sign In issue

Question

Azure AD B2C custom policy Sign In issue

Fispoke DevOps 20

Issue Description

I am implementing a custom policy in Azure AD B2C.

The same local user account is able to sign in successfully using a built‑in User Flow policy. However, when I attempt to sign in using a Custom Policy, the sign‑in fails.

Observed Behavior

When using the Custom Policy, clicking the Sign In button results in a frontend validation error:

Invalid username or password

At the same time, when I check the Azure AD B2C Sign‑in logs, the authentication status shows Success for the same sign‑in attempt.

Summary

✅ Sign‑in works correctly with User Flow policy
❌ Sign‑in fails with Custom Policy
❌ Frontend shows Invalid username or password
✅ Azure AD B2C Sign‑in logs show Success
Issue Description
I am implementing a custom policy in Azure AD B2C. The same local user account is able to sign in successfully using a built‑in User Flow policy. However, when I attempt to sign in using a Custom Policy, the sign‑in fails.
Observed Behavior
When using the Custom Policy, clicking the Sign In button results in a frontend validation error:

Invalid username or password
At the same time, when I check the Azure AD B2C Sign‑in logs, the authentication status shows Success for the same sign‑in attempt.
Summary
- ✅ Sign‑in works correctly with User Flow policy
- ❌ Sign‑in fails with Custom Policy
- ❌ Frontend shows Invalid username or password
- ✅ Azure AD B2C **Sign‑in logs show Success

Fispoke DevOps 20 Reputation points

2026-03-12T13:17:21.1+00:00

More details adding

Logs

Login Action
Request URL : https://fisadev.b2clogin.com/fisadev.onmicrosoft.com/B2C_1A_SignUpSignIn/SelfAsserted?tx=StateProperties=eyJUSUQiOiJlN2YxMTFkNC1hZDQ5LTQ1MzgtOTI0ZC1hMjA5N2E2MzgxZDkifQ&p=B2C_1A_SignUpSignIn
Payload :
tx

StateProperties=eyJUSUQiOiJlN2YxMTFkNC1hZDQ5LTQ1MzgtOTI0ZC1hMjA5N2E2MzgxZDkifQ

p

B2C_1A_SignUpSignIn

Response :
{status: "400", errorCode: "AADB2C90052", message: "Invalid username or password."}

How to fix this issue?
VEMULA SRISAI 9,430 Reputation points Microsoft External Staff Moderator

2026-03-12T16:36:21.25+00:00
Hello Fispoke DevOps ,

Based on the details and logs you shared, the request is reaching the Self-Asserted sign-in step of your policy B2C_1A_SignUpSignIn in Azure AD B2C** / **Microsoft Entra External ID:

/B2C_1A_SignUpSignIn/SelfAsserted

The response returned is:

400 - AADB2C90052: Invalid username or password

This error indicates that the credentials submitted on the sign-in page could not be validated against the user account stored in the directory.

You may want to verify the following:

Confirm the user exists in the tenant Ensure that the account being used to sign in is present in the directory and that the correct email/username is being entered.

Verify the sign-in identifier configured in the policy If your policy expects an email address but the user is entering a username (or vice versa), authentication will fail with this error.

Check the password Make sure the password entered is correct. If needed, try resetting the password using the Forgot password option within the same sign-in flow.

Review custom policy configuration (if applicable) Since the policy name B2C_1A_SignUpSignIn suggests a custom policy, verify that the authentication technical profile (commonly login-NonInteractive) is correctly configured and that the appropriate sign-in claim (such as email or signInName) is mapped correctly.

These checks typically resolve the AADB2C90052 authentication error during the Self-Asserted sign-in step.

1 answer

Your answer

Fispoke DevOps 20 Reputation points

2026-03-12T13:17:21.1+00:00

More details adding

Logs

Login Action
Request URL : https://fisadev.b2clogin.com/fisadev.onmicrosoft.com/B2C_1A_SignUpSignIn/SelfAsserted?tx=StateProperties=eyJUSUQiOiJlN2YxMTFkNC1hZDQ5LTQ1MzgtOTI0ZC1hMjA5N2E2MzgxZDkifQ&p=B2C_1A_SignUpSignIn
Payload :
tx

StateProperties=eyJUSUQiOiJlN2YxMTFkNC1hZDQ5LTQ1MzgtOTI0ZC1hMjA5N2E2MzgxZDkifQ

p

B2C_1A_SignUpSignIn

Response :
{status: "400", errorCode: "AADB2C90052", message: "Invalid username or password."}

How to fix this issue?
VEMULA SRISAI 9,430 Reputation points Microsoft External Staff Moderator

2026-03-12T16:36:21.25+00:00

Hello Fispoke DevOps ,

Based on the details and logs you shared, the request is reaching the Self-Asserted sign-in step of your policy B2C_1A_SignUpSignIn in Azure AD B2C** / **Microsoft Entra External ID:

/B2C_1A_SignUpSignIn/SelfAsserted

The response returned is:

400 - AADB2C90052: Invalid username or password

This error indicates that the credentials submitted on the sign-in page could not be validated against the user account stored in the directory.

You may want to verify the following:

Confirm the user exists in the tenant Ensure that the account being used to sign in is present in the directory and that the correct email/username is being entered.

Verify the sign-in identifier configured in the policy If your policy expects an email address but the user is entering a username (or vice versa), authentication will fail with this error.

Check the password Make sure the password entered is correct. If needed, try resetting the password using the Forgot password option within the same sign-in flow.

Review custom policy configuration (if applicable) Since the policy name B2C_1A_SignUpSignIn suggests a custom policy, verify that the authentication technical profile (commonly login-NonInteractive) is correctly configured and that the appropriate sign-in claim (such as email or signInName) is mapped correctly.

These checks typically resolve the AADB2C90052 authentication error during the Self-Asserted sign-in step.

Answer 1

RoryB 455

Do other custom policies work?

If this is a new installation, this error is sometimes because B2C has not been set up correctly.

https://learn.microsoft.com/en-us/azure/active-directory-b2c/tutorial-create-user-flows?pivots=b2c-custom-policy

There is a tool to do this:

https://b2ciefsetupapp.azurewebsites.net/

The other reason is that the "login-NonInteractive" technical policy in the extension file is not configured correctly.

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Azure AD B2C custom policy Sign In issue

Issue Description

Observed Behavior

Summary

Issue Description

Observed Behavior

Summary

1 answer

Your answer