Hello @Sean Thorne · Welcome to QnA platform and thanks for your query.
In your case, the error "The password has expired" is expected as when you reset users' password using the "Reset password" option in Azure ADB2C blade, it generates a temporary password which is marked as expired and must be changed at next sign-in but the B2C sign-in page doesn't support that. To sign in via B2C user flow, you must use permanent password. To generate permanent password, you need to sign-in to azure portal, enter the temporary password and you will be asked to set new password. The new password is permanent password and can be used to sign in via user flows. Which is why you should use this method of resetting the password only for the admin accounts who manage B2C tenant. For consumer identities, who sign-in to the consumer facing applications via user flows, password should be reset using "Password Reset user flow" only.
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