Hay... This worked

Code:
SQL> select account_status from dba_users where username='THOMAS';

ACCOUNT_STATUS
--------------------------------
EXPIRED

SQL> select password from dba_users where username='THOMAS';

PASSWORD
------------------------------
063D8DE086C2860D

SQL> alter user thomas identified by values '063D8DE086C2860D';

User altered.

SQL> select account_status from dba_users where username='THOMAS';

ACCOUNT_STATUS
--------------------------------
OPEN
SQL> conn thomas/thomas
Connected.