ORA-12504: TNS:listener was not given the SERVICE_NAME in CONNECT_DATA

@localhost

There are many suggestions provided related to this in forums, but I tried them but none worked for me.

My Service name is ADVA.

The problem started when I try

Sqlplus /@localhost

C:\Windows\system32>sqlplus /@localhost

SQL*Plus: Release 19.0.0.0.0 - Production on Thu Aug 13 04:54:39 2020
Version 19.3.0.0.0

Copyright (c) 1982, 2019, Oracle.  All rights reserved.

ERROR:
ORA-12504: TNS:listener was not given the SERVICE_NAME in CONNECT_DATA

Enter user-name:

I tried multiple modifications to my tnsnames.ora and listener.ora, but none could help me resolve this error.

Below are my configurations.

C:\oracle\product\19.0.0\db_1\network\admin

tnsnames.ora

ORACLR_CONNECTION_DATA =