If Canonical name is maintained in lower case, the system doesn’t recognize it. In our case when user tries to login they receive an error that user doesn’t exist with SNC user name. For already existing users with lower case SNC there is no error. The issue is only for newly created users or users whose SNC is modified. New users are created in SAP with password. For now we downgraded QAS to 4.1.7 since this problem is not manifesting on this version.