The requested URL /OA_HTML/AppsLogin was not found on this serve

All the AP services are started successfully, but the login page can not open.

Solution:

This problem occurred because wsrp_service.wsdl was owned by root but the services were being started by applmgr.
Ensure that the file
$ORA_CONFIG_HOME/10.1.3/j2ee/oacore/application-deployments/oacore/html/server-wsdl/wsrp_service.wsdl
it shows it is owned by root. Somebody started the services of Apps as root user
Changed the owner of the file to Apps Owner.
Restarted the service.