Hi Tom,
I'm facing a problem when trying to use remote debug feature in SQL Developer, I appended an ACE as recommended and granted execution permissions on the DBMS_DEBUG_JDWP package for my app schema MY_SCHEMA and the Apex Schema as well.

BEGIN
      dbms_network_acl_admin.append_host_ace(
            host=>'*.mydomain.com',
            ace=> sys.xs$ace_type( 
                  privilege_list=>sys.XS$NAME_LIST('JDWP'),
                  principal_name=>'MY_SCHEMA', --Appended also for APEX_050100
                  principal_type=>sys.XS_ACL.PTYPE_DB
            ) 
      );
      COMMIT;
END;

So, when I start listening on SQL Developer I can connect and remote debug from another session of SQL*Plus or maybe Toad without issues. But for some reason it's not working directly from an APEX application, even when the application is pointing to one of the schemas I granted access, for example MY_SCHEMA. I always get "ORA-01031: insufficient privileges” error.

--Remote debug test
DECLARE
    lv_source VARCHAR2(500);
BEGIN
    DBMS_DEBUG_JDWP.CONNECT_TCP('MyPCName.mydomain.com', 4000);
    lv_source := PKG_MYPACKAGE.AnyFunction('XXYYZZ');
    DBMS_DEBUG_JDWP.DISCONNECT;
END;

I've been trying to find the root cause for a while but no success. Also in internet there is not enough information, so no idea what's going on. Any help or clue will be appreciated, thanks.

I'm using:
APEX 5.1.0.00.45
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production