A. They did not enable the ora_p2_dblistener access rule for port 1521.

B. SQL*Net is not supported in Oracle Database Cloud Service.

C. They need to create a custom security rule allowing SQL*Net access to their database instance.

D. They did not enable ora_p2_dbconsole for Enterprise Manager access.

E. They need to install the SQL*Net access pack before they can use that product.