ORA-12638: Credential retrieval failed

Authentication Methods Available with Oracle Net Services:

SQLNET.AUTHENTICATION_SERVICES

NONE: for no authentication. Valid username/password need to access db.
ALL: for all authentication methods
NTS: for window authentication

Solution:
You need to go the the %ORACLE_HOME%\network\admin location:

eg E:\oracle\dbhome_1\network\admin folder

On check, I found following line in sqlnet.ora file

SQLNET.AUTHENTICATION_SERVICES= (NTS)

Then modified the above line and it resolved problem:

SQLNET.AUTHENTICATION_SERVICES= (NONE)