This article was created in response to a support issue logged with K2. The content may include typographical errors and may be revised at any time without notice This article is not considered official documentation for K2 software and is provided “as is” with no warranties.

Issue

The user receives the following error when trying to access Smartforms:

"124777","2018-05-18 03:05:16","Error","General","28083","ExtenderExecuteError","ProcessInstance.HandleException","28083 ServerEvent: Authentication With Server Failed : The logon attempt failed
InnerException: An unexpected error has occured while trying to resolve a value for Resolver ID 59F5D9BC-3B14-45ca-9C94-6FCB3C4D862F.
InnerException: Authentication With Server Failed : The logon attempt failed","","","<HOSTSERVER>:D:\Program Files (x86)\K2 blackpearl\Host Server\Bin","124777","d3f8233e7ab14e44a068eab53d055ca8",""

Symptoms

The issue could be caused by "DisableloobackCheck" not being enabled on the K2 server.

Troubleshooting Steps

To resolve this issue, re-enable "DisableloopbackCheck" on the server.

Read more here: 
https://support.microsoft.com/en-us/help/896861/you-receive-error-401-1-when-you-browse-a-web-site-that-uses-integrate