The following information can help when troubleshooting the server installation.
For problems logging in, check the server pages on the server computer.
Click Connection > Login Parameters, and then click Test.
Click the Test HTML Access, Test Webservice Access, and Test Database Access buttons and see if all tests pass.
If Test HTML Access returns an error code, but Test Webservice Access is successful, you can ignore the error. The error may be raised because the web server is not configured to handle http, or the page is restricted.
If Test Webservice Access fails, you can use Test HTML Access to see if you can connect to the server machine at all. Even if it returns error 401 like in the following picture, it means that the web server responds on call of the URL given in the login parameter, which can be treated as a success.
If there is an error with database access, then it might help to reboot the server computer after the tnsnames.ora and sqlnet.ora files have been copied to the server directory.
If there is an error at application startup and all login parameter tests are successful, check the security access settings of the server installation directory.
Sometimes the IIS_IUSRS user is not in the list. In this case, click Edit, and then click Add on the Security tab.
Then, type IIS_IUSRS, and click OK.
Select the Read & execute option, click Apply, and then click OK.