Thank you for posting this in Microsoft Q&A.
I understand that you are trying to reset the password from the Azure AD B2C portal. However, when attempting to use the temporary password in the sign-in user flow, you are encountering the error message "The username or password is invalid" or "The password has expired."
When you reset the password using an admin account from the Azure AD B2C portal, a temporary password is generated. This password is marked as expired and requires the user to set a new one. This is expected behavior as Azure AD B2C sign-in policies don't support signing in with a temporary password by default and instead use a different mechanism for resetting passwords (e.g., Password Reset User Flows or Custom Policies).
To allow users to perform a self-service password reset, please use the Password Reset flow: https://zcusa.951200.xyz/en-us/azure/active-directory-b2c/add-password-reset-policy?pivots=b2c-user-flow
Additionally, you can enable the Force Password Reset User Flow here: https://docs.microsoft.com/en-us/azure/active-directory-b2c/force-password-reset?pivots=b2c-user-flow
Hope this helps. Do let us know if you any further queries.
Thanks,
Navya.
If this answers your query, do click Accept Answer
and Yes
for was this answer helpful. And, if you have any further query do let us know.