Symptoms

Currently we are unable to access the K2 Designer site from the K2 Server itself (locally). However, it can be accessed on other machines with no issue. When we open the K2 Designer site locally we see the following error:

HTTP Error 401.2 - Unauthorized
You are not authorized to view this page due to invalid authentication headers.

Most likely causes:
-No authentication protocol (including anonymous) is selected in IIS.
-Only integrated authentication is enabled, and a client browser was used that does not support integrated authentication.
-Integrated authentication is enabled and the request was sent through a proxy that changed the authentication headers before they reach the Web server.
-The Web server is not configured for anonymous access and a required authorization header was not received.
-The "configuration/system.webServer/authorization" configuration section may be explicitly denying the user access.
 

Diagnoses

This is most likely an issue with the IIS settings on the K2 designer site. Specifically there is some configuration that does not allow a local user to access the site. This could be due to the specific account or even the authentication protocol.

We ran through the recommended steps on this error page first as they are most useful and will usually result in a solution:

-Verify the authentication setting for the resource and then try requesting the resource using that authentication method.
-Verify that the client browser supports Integrated authentication.
-Verify that the request is not going through a proxy when Integrated authentication is used.
-Verify that the user is not explicitly denied access in the "configuration/system.webServer/authorization" configuration section.
-Create a tracing rule to track failed requests for this HTTP status code. For more information about creating a tracing rule for failed requests, click here (http://www.iis.net/learn/troubleshoot/using-failed-request-tracing/troubleshooting-failed-requests-using-tracing-in-iis).
 

Resolution

Customer found that the following steps resulted in a solution to this issue:

1. Clear IE browser cache
2. Uncheck IE auto detect proxy setting
3. Add local server to trusted zone
4. Custom zone and checked promote my input user name password.
5. Run K2 SmartForms configuration

These steps were repeated on another server and we found the issue was solved on that server as well.