_SYS_REOP user is a system user, and is always active at system level, so we don't need to re-activate it.
For more details please refer:
http://help.sap.com/hana/SAP_HANA_Administration_Guide_en.pdf >> section 7.1
http://help.sap.com/hana/SAP_HANA_Security_Guide_en.pdf >> Section 5.3
Regards
Kumar 