clusters unknown status with Klusterlet Registration Degraded and expired bootstrap secret

Issue

• clusters unknown status when Klusterlet Registration Degraded . Deleting the Klusterlet and recreate it does not recover the managed cluster .
  followed "1.22.3. Resolving the problem: Klusterlet is in the degraded condition"
  https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.6/html-single/troubleshooting/index#troubleshooting-klusterlet-with-degraded-conditions