When running the Registration Wizard, the below error is shown:
Exception of type 'System.Web.HttpUnhandledException' was thrown.
Argument 'userFqn' may not be null or empty
Parameter name: userFqn"
It was determined that the SharePoint farm and the account running the Registration Wizard was in a different domain and this domain had not yet been configured in K2.
These errors were also logged in the HostServer logs:
Check and add the missing domain if applicable:
K2 Management Site > Users > K2 > Domains
K2 Workspace > Management Console > User Managers > K2 > Domains
* A restart of the K2 Blackpearl service/console is required.