APEX - ORDS   Errors: 404 NOT FOUND,
             REST DATA SERVICE NOT AVAILABLE,
             REQUEST CANNOT BE MAPPED to DATABASE.                                          

Sometimes the ORACLE REST DATA SERVICES shows some of the  below unexpected and annoying errors which prevents to launch Oracle Apex Instances:

• 404 Not found
• REST  data service not available
• The request could not be mapped to any database…..

and so on

I found the below solution and you can try to get rid of from this annoying issue:

1. login to SYS with SYSDBA privilege and execute the below command to unlock & Reset password for below users.
2. Also if you update the wrong password , it will not be in sync with ords and causes you below errors like below. So make sure you get the correct password as i wasted one day by updating wrong password.

<Jun 13, 2018, 9:09:23,441 AM EDT> <Error> <oracle.dbtools> <BEA-000000> <The username or password for the connection pool named apex_rt, are invalid, expired, or the account is locked

oracle.dbtools.common.jdbc.ConnectionPoolConfigurationException: The username or password for the connection pool named apex_rt, are invalid, expired, or the account is locked

FIX:

alter user APEX_LISTENER identified by welcome1 account unlock;

alter user APEX_REST_PUBLIC_USER identified by welcome1 account unlock;

alter user APEX_PUBLIC_USER identified by welcome1 account unlock;

alter user ORDS_PUBLIC_USER identified by welcome1 account unlock;

    3. Restart the ORDS Services once done.