Tring to change the user password to an old one, it failed:
SQL> alter user tester identified by "Welcome123#test";
alter user tester identified by "Welcome123#test";
*
ERROR at line 1:
ORA-28007: the password cannot be reused
SOLUTION
Check the profile used by user tester.
SQL> alter profile default limit PASSWORD_REUSE_MAX unlimited;
Profile altered.
SQL> alter user tester identified by "Welcome123#test";
User altered.
SQL> alter profile default limit PASSWORD_REUSE_MAX 10;
Profile altered.
SQL> alter user tester identified by "Welcome123#test";
alter user tester identified by "Welcome123#test";
*
ERROR at line 1:
ORA-28007: the password cannot be reused