Oracle 12c - Insufficient Privileges When Trying To Create A Trigger With SYS User
Even if you create the trigger as SYS, the owner must have the CREATE TRIGGER privilege:
GRANT CREATE TRIGGER TO CRE;
In addition to the above, to create an AFTER LOGON ON DATABASE trigger, the ADMINISTER DATABASE TRIGGER privilege is also required:
GRANT ADMINISTER DATABASE TRIGGER TO CRE;