OktaAspNetExample AccessToken Not Found

I am trying to get a .net mvc application setup to connect to Okta using OIDC. To that end I am playing with the OktaAspNetExample application. We have setup the application in Okta and when i run the application i get to the login screen. However, after the login happens and i try to view the TokenResponse in the startup.cs class, I get the exception at the tokenResponse.IsError propery. Looking at the tokenResponse, the AccessToken is null and the Error is “Not Found”. We have looked at all the setting in the Okta application and they appear to be set correctly. Can you offer any advice as to what the issue may be?