The error below means that Azure could not find the connectedCluster ARM resource associated with your cluster:
autorest/azure: Service returned an error. Status=404 Code="ResourceNotFound" Message="The Resource 'Microsoft.Kubernetes/connectedClusters/my-workload-cluster' under resource group 'AKS-HCI2' was not found. For more details please go to https://aka.ms/ARMResourceNotFoundFix"]
You may encounter this error if:
You supplied an incorrect resource group or subscription while running the Disable-AksHciArcConnection cmdlet.
You manually deleted the resource on the Azure portal.
ARM cannot find your Azure resource.
To resolve this error, as indicated in the error message, see resolve resource not found errors.