How to import orphaned cluster without kubeconfig

I created an HA cluster using RKE 0.1.13 some time ago, then used that cluster to create another custom cluster (Add Cluster -> From Existing Nodes).
This newer sub cluster has a production workload.
The first cluster was lost and is unrecoverable.
I have built a new primary HA cluster using the same RKE version and setup method and am now attempting to import the existing sub cluster via Add Cluster -> Import an Existing Cluster
I have a kubeconfig for this sub cluster but it references the old cluster and the old user.

When I attempt to use the old kubeconfig:
unable to recognize “https://servername-removed/v3/import/removed.yaml”: the server has asked for the client to provide credentials

Is it possible to import the user information from the old kubeconfig to the new primary cluster?