How to resolve "AADST55203" error: Multi-factor authentication configuration blocked

{     "error": "access_denied",     "error_description": "AADSTS55203: Configuring multi-factor authentication method is blocked. Trace ID:  Correlation ID:  Timestamp: 2025-09-17 20:48:30Z",     "error_codes": [         55203     ],     "timestamp": "2025-09-17 20:48:30Z",     "trace_id": "",     "correlation_id": "",     "suberror": "provider_blocked_by_rep" }

SMS authentication method was previously configured in our B2C Entra and was functioning correctly until last week, when it suddenly stopped working. Currently, users can only authenticate via email. Conditional Access policy is also in place that requires Multi-Factor Authentication (MFA).