In some cases when upgrading from K2 Five (5.0) to K2 Five (5.1) running the Registration Wizard will fail and display the following error:
HTTP Error 500.19 - Internal Server Error
After this is hit sequential runs will not render anything.
Unable to complete the Registration Wizard after upgrading to K2 Five (5.1).
This is a known issue, please contact K2 Support and request K2 Five (5.1) Fix Pack 1.