When the error is 500, that means it's an internal error, meaning internal to the service - the service threw an exception that was not caught.
Look in the Windows event logs
on the server to see what went wrong.
- Go to menu Tools/Internet Options in your IE.
- Click on the Advanced tab, uncheck
"Show friendly HTTP error messages" option and click Ok.
- Try accessing your web page again. Now you will see much more meaningful error message which will help you to troubleshoot the problem.
Other few possibilities:
There might be an issue in the way you have hosted your app. May be multiple config files?
Do make sure, you have hosted your application correctly. Published the application as website and setting up the virtual directory.
Read about Error 500 here:
HTTP Error 500 Internal server error
500 Internal Server Error
See details here: Microsoft Support: Error message when you visit a Web site that is hosted on IIS 7.0: "HTTP Error 500.0 – Internal Server Error"