Check whether em is enabled or not.
Note: if output 0 means, emexpress disabled

select dbms_xdb.getHttpPort() from dual;
select dbms_xdb_config.getHttpsPort() from dual;

Enable emexpress with https

SQL> exec dbms_xdb_config.sethttpsport(5500);

Enable emexpress with http

SQL> exec dbms_xdb_config.sethttpport(8080);

Disable em express (set port to 0)

SQL> exec dbms_xdb_config.sethttpsport(0);
SQL> exec dbms_xdb_config.sethttpport(0);