Getting ORA-01017: invalid username/password; logon denied no matter what I do

Hello,

HOST IS => NAME="Red Hat Enterprise Linux Server"

VERSION="7.7 (Maipo)"

I've installed Oracle 19c with patch 10. Following is the registry entry :

SQL> select comp_name, version_full,status from dba_registry ;

COMP_NAME                VERSION_FULL          STATUS

---------------------------------------- ------------------------------ --------------------------------------------

Oracle Database Catalog Views      19.10.0.0.0          VALID

Oracle Database Packages and Types    19.10.0.0.0          VALID

Oracle XML Database           19.10.0.0.0          VALID

Oracle Real Application Clusters     19.10.0.0.0          OPTION OFF

Oracle Workspace Manager         19.10.0.0.0          VALID

I've been able to login into the using "/ as sysdba". I 've created an application container. Also created a common user "c##mdusr" identified by testmcd123 in Root CDB.

I've started the listener service and see that the service name is correct "eqtscdb1.eqdomain.com".