Symptoms

Client was experiencing issues installing K2 for SharePoint. First issue was related to the installer throwing a "Could not connect to URL" error on K2 for SharePoint. Second issue was related to having an HTTPS site for SharePoint and the third error was in registering of a SharePoint site. SharePoint Service Broker would error out with:
Validation the remote server returned an error: (403) Forbidden.Failed to initialized the Context URL: http://zeus Username: Error Details: Method
SharepointService.initializeContext
 

Diagnoses

The first issue was related to DNS, the second issue was related to a non HTTPS SharePoint site, and the third issue was related to a script that needed to be run on the sharepoint front end server.
 

Resolution

Client fixed their DNS issue by rebuilding their environment. The sharepoint issue was fixed by leaving the default https binding in place when going through the installers. The third issue was fixed when we changed SharePoint 2013 to use OAuth over HTTP by running the following code on the SharePoint front end server:

$c = Get-SPSecurityTokenServiceConfig
$c.AllowMetadataOverHttp = $true
$c.AllowOAuthOverHttp= $true
$c.Update()