DesktopStudio_ErrorId : ProvisioningTaskError
ErrorCategory : NotSpecified
ErrorID : FailedToCreateImagePreparationVm
TaskErrorInformation : Terminated
InternalErrorMessage : The given key was not present in the dictionary.

Provide permissions for the Service Account being used for XenDesktop Host Connection as per https://docs.citrix.com/en-us/xenapp-and-xendesktop/7-15-ltsr/install-configure/install-prepare/vmware.html 

We need to ensure that these permissions are provided on vCenter as well as DataCenter Level and propagated to the VMWARE Distributed Switch level as well so as to allow MCS to be able to configure the Network Adapter w.r.t to the defined VLAN on the MCS created Preparation VM and do the same for subsequent MCS created VDA Machines. 

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Problem Cause

Insufficient previleges on VMWARE Distributed Switch Level causes this exception where XenDesktop cannot modify the Network Adapter settings on the Preparation VM and hence we get the failure point while create the Preparation VM and encounter an error "The given key was not present in the dictionary" because of the permission issue. 

While creating a new MCS Machine Catalog, we encounter an error with the InternalErrorMessage: The given key was not present in the dictionary