On clicking Start the automatic upgrade, the following error message appears:
“The service instance is already registered with the configuration service”

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Mandatory Upgrade

 

It could happen after :

  • Adding a new controller to the farm
  • Changing the XML service port
  • Migrating to XenDesktop 7.6

Details of the error XDDS:C266BBDF

How to fix the error XDDS:C266BBDF ?

  • Close Desktop Studio
  • Backup you database (optional)
  • Run the following commands in PowerShell on one of the DDC:

  • Run the following commands in PowerShell on all DDC (optional)

  • Start Desktop Studio
  • Run through the upgrade process within Studio.

This is also documented here:
http://support.citrix.com/article/CTX200446