Problem
Running the Registration Wizard fails on the Application step and returns a NOTFOUND error.
From the host server log, a (404) Not Found error message is returned when trying to get information on existing group providers:'Error','General','0','ErrorMessage','IntegrationService.Execute','0 System.Net.WebException: NOTFOUND ---System.Net.WebException: The remote server returned an error: (404) Not Found.at System.Net.HttpWebRequest.GetResponse()at SourceCode.SmartObjects.Services.SharePoint15.Common.Helpers.ConfigHelper.GetSPSiteInfo(String siteUrl)--- End of inner exception stack trace ---at SourceCode.SmartObjects.Services.SharePoint15.Common.Helpers.ConfigHelper.GetSPSiteInfo(String siteUrl)at SourceCode.SmartObjects.Services.SharePoint.Integration.Execution.Execute.ManageExistingSPLabelGroupProvider(String siteUrl, Boolean isOnlineSite, String resourceGuid, String realm)at SourceCode.SmartObjects.Services.SharePoint.Integration.Execution.Execute.ManageSPLabelGroupProvider(ServiceInstance Service)at SourceCode.SmartObjects.Services.SharePoint.Integration.IntegrationService.Execute(). Additional info: IntegrationService.Execute.'
Solution
Check the group providers in K2 Management/Users/SP to confirm that all the listed SharePoint URLs are valid. You may remove those that point to invalid sites.