How to resolve ORA-12514/12545 when I executed "sqlplus" in my Linux Server installed OracleClient19

Dear Oracle Support,

I hope this message finds you well.

I configured the tnsnames.ora file as follows in my Linux Server installed OracleClient19.

Then, I executed the tnsping command as follows and confirmed that an "OK" message was
returned.

$ORACLE_HOME/bin/tnsping DB_TEST

However, when I executed the sqlplus command as follows, I encountered the ORA-12514 error.

$ORACLE_HOME/bin/sqlplus DB_TEST_USER/DB_TEST_PAWD@DBTEST

Then, when I enter the username and password again, the ORA-12545 error occurs.

Could you please advise on how to resolve these errors?

Best Regards,