Symptoms

Unable to run the K2 for SharePoint Registration Wizard:
A smartforms designer site could not be found in the autodiscover results
 

Diagnoses

Smartforms Designer URL has set autodiscovery to true. However, the value of the field is pointing to an SSL-enabled site. Their SharePoint is not using SSL. As per documentation, HTTP-HTTP and HTTPS-HTTPS for both Designer and SharePoint are the only supported schemas.

http://help.k2.com/onlinehelp/K2ForSharePoint/ICG/4.6.11/default.htm_Install_Topics/Before/SecurityAuth.htm?TocPath=Prepare|_____3
 

Resolution

Re-ran the smartorms setup manager to update the binding of the Designer site to use HTTP as SharePoint is not using SSL.