1) Login to your Oracle Database using admin privileges:
cmd> sqlplus / as sysdba
or
cmd> sqlplus system/{systemPassword}@{OracleSID}
2) Unlock your user's account using the following command:
sql> alter user {yourDbUser} account unlock;
3) Still in SQL*Plus command prompt, prevent account locks to not occur again:
sql> ALTER PROFILE "DEFAULT" LIMIT PASSWORD_LIFE_TIME UNLIMITED;
sql> ALTER PROFILE "DEFAULT" LIMIT FAILED_LOGIN_ATTEMPTS UNLIMITED;
Edit due comment
The above instructions should solve your problem. I'm posting an additional command I've found related to this subject you can try (I'm not confident it is the solution though):
sql> grant connect, resource to {yourDbUser};
You can also check for the status of other locked users in your database. Maybe your tool is trying to connect with some other user that, besides the one you are using, still have this issue.