APEX 21.1.v1 on a RDS Oracle 19c se2 instance

I'm trying to install APEX 21.1.v1 on a RDS Oracle 19c se2 instance. I cant understand why but seems that applying option group, it does not correctly configure the ADMIN user and the INTERNAL workspace.

The result is that I'm unable to login with ADMIN account or reset correctly the password. I can create the ADMIN account by hand with this script:

BEGIN
  wwv_flow_api.set_security_group_id(p_security_group_id=>10); 
  wwv_flow_fnd_user_api.create_fnd_user( 
    p_user_name     => 'ADMIN', 
    p_email_address => 'mail@aaa.com',
    p_web_password  => 'secretpass') ; 
END;
/
COMMIT
/

But it's not able to login correctly and displays error: ERR-7620 Could not determine workspace for application ()

It's weird because I've already installed others APEX 19.1.v1 instances flawlessly.

The only way I've found to install APEX 21.1.v1 is to do an upgrade from version 19.1.v1.

Any hints?