I'm getting reacquainted with Oracle after several years and Oracle 18 XE is causing some problems. I use SQLDeveloper to connect as the SYSTEM user. Then when I create a new user cpp it says that is an invalid user name. I have to prefix new users with c##, so I created the user c##cpp. The c##cpp user is there under Other Users.

But when I try to create a new connection as the c##cpp user the connection fails. I've also tried creating the connection as just cpp, but that fails too.

What's up with creating users in Oracle 18 XE?

-------Update showing my connection parameters-------

[![enter image description here](https://i.stack.imgur.com/Lb63j.png)](https://i.stack.imgur.com/Lb63j.png)

I get the same error if I try to connect with SID XE.