Identiy Server 4

I have identity server 4 running.
Client application is registered and want to communicate with server,it works fine.If we have  "UI/{0}/Views/{1}.cshtml" format.
but if we use default structure it still return the above format to find view and result is not found with 404 status.

My question is when request for token comes to identity server which class is responsible to give redirection url or view which is login if unauthorized access.