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