how to enable flashback constraints

I have created several non-container 12c databases, 12.1.0.1.0 using dbca and manually.  In all of them I have found disabled constraints on flashback tables.

OWNER      CONSTRAINT_NAME                C TABLE_NAME                     STATUS

---------- ------------------------------ - ------------------------------ --------

SYS        SYS_C001728                    U SYS_FBA_FA                     DISABLED

SYS        SYS_C001736                    U SYS_FBA_TRACKEDTABLES          DISABLED

SYS        SYS_C001739                    U SYS_FBA_USERS                  DISABLED

SYS        SYS_C001744                    U SYS_FBA_BARRIERSCN             DISABLED

SYS        SYS_C001770                    U CLI_LOG$                       DISABLED

How do I enable these constraints?  I tried utlrp and it didn't enable them.  Not allowed to do it manually.

SQL> alter table SYS."SYS_FBA_FA" enable constraint "SYS_C001728";