If database is down url will show the error 404. So check whether your database is up and running. Also try restarting OATS server services.
I had the same problem. I installed OATS 188.8.131.52 on Windows 2K8 R2, and used Oracle XE 11.2 as the local database to get the increased 11GB of User storage space. The system was humming along smoothly for about 3 months, then all of a sudden, I get 404's for OTM, OLT, and Admin. The only thing that appears to function is "Get Started With Oracle Database 11g Express Edition". The only errors I see were in \OracleATS\oats\servers\AdminServer\logs\oats.log: Unable to resolve 'OATS_common_DS'. Resolved ''; remaining name 'OATS_common_DS', AND Received exception while creating connection for pool "OATS_common_DS": ORA-28001: the password has expired.
At this point every forum I have read, user's end up uninstalling/reinstalling OATS, and it works again. C'mon.... really?!?!?!
The issue is with Oracle XE 11 database defaults all passwords set to expire after 180 days, and does not differentiate between service accounts and user accounts. Check your service accounts:
Click Start\All Programs\Oracle Database 11g Express Edition\RUN SQL Command Line
CONNECT SYS/password AS SYSDBA
select username,account_status,expiry_date from dba_users;
Check to see if the default OATS service accounts (OTM, OLT, and OATS) have expired.
To set Password Expiry Date to unlimited:
select * from dba_profiles where resource_name in ('PASSWORD_LIFE_TIME','PASSWORD_GRACE_TIME');
alter profile default limit password_life_time unlimited;
alter profile default limit password_grace_time unlimited;
Check Service accounts again. EXPIRY_DATE should be blank.
Try your OLT, OTM, and Admin again to see if your 404's are gone.
In cmd use the following commands...
sqlplus / as sysdba;
alter database open;
If any errors shown let me know....