Report Server URL Not Valid Error

I have an application that needs the report server URL for that application's sql instance. The Report Server installation was a default installation, with an instance name, therefore the report server URL should be:
http://servername/reportserver$InstanceName
When I enter the above, on the server that has the SQL server instance, the web-page displays just the report server URL and report server version number.

However, when I enter the above URL in the application, it returns an error stating:

The Report Server URL entered is not valid

Following is the URL for the reports manager, which the application accepts:

http://servername/reports$InstanceName
Does anyone know what is or could be wrong with the report server URL and how to fix the issue(s)?

Thanks.