1. Go to the client home location where you are tried to connect the Oracle Server. Path = ORACLE_CLIENT\network\admin
2. SQLNET.ORA is client file. So, we need to enable trace at client side.
3. Open the SQLNET.ORA file of client and set the following parameter to enable trace.

TRACE_LEVEL_CLIENT=16
TRACE_DIRECTORY_CLIENT=C:\trace
TRACE_UNIQUE_CLIENT=ON
DIAG_ADR_ENABLED =OFF   

4. then try to connect again for reproduce the error:

--Specify direct tns name configure in TNSNAMES.ORA file
SQLPLUS username@<tns_alias>

--Easy connect
SQLPLUS username@"(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=server_hostname_here)(PORT=listener_port_here))(CONNECT_DATA= 
                      (SERVICE_NAME=service_name_here)))"

5. Check the directory location for see the log files:

TRACE_DIRECTORY_CLIENT=c\trace\*.trc
Trc file is generated. Open and check the error.

6. Disable the Trace by commenting or deleting the entered line in SQLNET.ORA file in step 3.