Oracle DB "ERROR: ORA-12154: TNS:could not resolve the connect identifier specified"

Question

Good day folks. I need help understanding exactly what this error means and how I should go about solving it. I installed Oracle Database 21c Express Edition yesterday and I was given this error ERROR: ORA-12154: TNS:could not resolve the connect identifier specified after entering the username and password information in CMD. Essentially the code in CMD looked as follows:

SQL*Plus: Release 21.0.0.0.0 - Production on Tues Oct 24 14:47:54 2023
Version 21.3.0.0.0

Copyright (c) 1982, 2021, Oracle.  All rights reserved.

Enter user-name: system
Enter password:
ERROR:
ORA-12154: TNS:could not resolve the connect identifier specified

I set the following environmental variables ORACLE_HOME to the path where the Oracle XE is installed, ORACLE_SID to XE and TNS_ADMIN to the same path as ORACLE_HOME/network/admin. From there, I also noticed that none of the following files were in ORACLE_HOME/network/admin: tnsnames.ora, sqlnet.ora and listener.ora. I then searched for "tnsnames.ora" and found that all of these files were stored under C:\app\user1\product\21c\homes\OraDB21Home1\network\admin. I opened them and found all the information to be there and correct, so I copied those files and pasted them into directory where they should have been in the first place.

I opened up CMD and tried again, but no success, exactly the same error popped up again.

The contents of the tnsname.ora file:

# Generated by Oracle configuration tools.

XE =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = DESKTOP-1)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = XE)
    )
  )

LISTENER_XE =
  (ADDRESS = (PROTOCOL = TCP)(HOST = DESKTOP-1)(PORT = 1521))


ORACLR_CONNECTION_DATA =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
    (CONNECT_DATA =
      (SID = CLRExtProc)
      (PRESENTATION = RO)
    )
  )

The contents of the sqlnet.ora file:

# sqlnet.ora Network Configuration File: C:\app\user1\product\21c\homes\OraDB21Home1\NETWORK\ADMIN\sqlnet.ora
# Generated by Oracle configuration tools.

# This file is actually generated by netca. But if customers choose to 
# install "Software Only", this file wont exist and without the native 
# authentication, they will not be able to connect to the database on NT.

SQLNET.AUTHENTICATION_SERVICES= (NTS)

NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)

Lastly, the contents of the listener.ora file:

# listener.ora Network Configuration File: C:\app\user1\product\21c\homes\OraDB21Home1\NETWORK\ADMIN\listener.ora
# Generated by Oracle configuration tools.

DEFAULT_SERVICE_LISTENER = XE

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = CLRExtProc)
      (ORACLE_HOME = C:\app\user1\product\21c\dbhomeXE)
      (PROGRAM = extproc)
      (ENVS = "EXTPROC_DLLS=ONLY:C:\app\user1\product\21c\dbhomeXE\bin\oraclr.dll")
    )
  )

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = DESKTOP-1)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )

I then also conducted a tnsping test and the status was OK and displayed the tns information.

So, if there are no syntax errors, and the database is visible, why am I not able to login to it? Why were the three .ora files not created in the right directory? I am genuinely stumped.

Apologies for the long question. I just figured the more detail, the better. Any help would be greatly appreciated.