[KBA-79172] "Access denied: Unknown credential" event for an expired cardholder that is reactivated in Security Center 5.11.3.5 - This article explains why when you reactivate an expired cardholder after the Access Manager role starts, the cardholder does not get synchronized to the access control unit. - Security Center 5.11.3.5

After upgrading to Security Center 5.11.3.5, when reactivating an expired cardholder after the Access Manager role starts, the cardholder does not get synchronized to the access control unit. This causes the cardholder to be denied access with the Unknown credential reason when presenting a credential to a reader.