Error ORA-12505 when connecting to Database Oracle 11g SQL Developer
The way you are connecting to the database (connection type "basic") isn't using your tnsnames.ora file at all. It is using a basic JDBC connect string - which is fine. That said, the error indicates that the database "xe" hasn't registered with the listener, meaning that the database itself probably isn't running at all. Check to make sure that your database instance is actually up. Check this document for details: https://docs.oracle.com/cd/E17781_01/admin.112/e18585/toc.htm#XEGSG101