You are unable to log in to Aurea Monitor Intermediary (AI) with a local user when a user with the same name but a different password exists in the LDAP directory.
The authentication with LDAP fails due to password mismatch, but AI apparently is not falling back to a local user account (it is not checking the local user list and not trying to authenticate against the local user).
This is a known issue and reproducible even in version 12.0 (version 2021 R1).
The issue has been fixed in version 2021 R1 HF2 (12.00.02). Please upgrade to 2021 R1 HF2 or a later version.
Agent-only: More details in ACTA-60401.
The same issue has been reported previously here: Login to AI console with local user doesn't work when AD Authentication fails