Studio Error: An unknown error has occurred. The given key is not present in the dictionary - after evicting controllers. XDDS:55D5CDB2.

Four working DDCs and two non-working DDCs are present in the environment.

Evicted two working DDCs from site:

• As controller software was removed from these servers prior to eviction, generated the evict script from a working controller.
• Modified the evict.txt file and added the non-working controller machine accounts and SIDs.

Studio is still not functioning after eviction.

Ran Get-ConfigRegisteredServiceInstace | Measure 

For a 7.9 broker, we should have 55 services per server - Total of 220.

In this case it shows 275 services, indicating removed broker services are still registered.

Ran Get-ConfigRegisteredServiceInstance | select serviceaccount, serviceinstanceuid | sort-object -property serviceaccount > c:\registeredinstances.txt to find the UID of registered services for the evicted controllers. The command was run on a working controller and the evicted controller did not run the command. (404 not found error)

One of the two evicted controllers had 55 registered instances.

Ran Unregister-ConfigRegisteredServiceInstance -serviceinstanceuid <UID> on the working controller to unregister service instances of non-working controller.

Studio is functional again and the four working controllers are listed.

Problem Cause

Orphaned Controllers and Service instances causing Studio and Director not to function.

Error: An unknown error has occurred - The given key was not present in the dictionary.

https://www.citrix.com/blogs/2013/10/22/xd-tipster-removing-controllers-from-an-xd-site-using-posh/.