ORA-01927: cannot REVOKE privileges you did not grant

From the view DBA_HOST_ACES, I can see the privilege 'CONNECT' has been granted to JHSC.

SQL> show user

USER is "SYS"

SQL> SELECT * FROM DBA_HOST_ACES;

HOST                           LOWER_PORT UPPER_PORT  ACE_ORDER START_DATE                     END_DATE                       GRANT INV PRINCIPAL            PRINCIPAL_T PRIVILEGE

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

*                                                             1                                                               GRANT NO  GSMADMIN_INTERNAL    DATABASE    RESOLVE

mail.mydomain                          25         25          1 03-JUL-18 02.07.34.000000 PM                                  GRANT NO  JHSC                 DATABASE    CONNECT

SQL> EXEC dbms_network_acl_admin.remove_host_ace(host=>'mail.mydomain',ace=>xs$ace_type(privilege_list=>xs$name_list('connect'),principal_name=>'JHSC',principal_type=>xs_acl.ptype_db));