RKE Rancher UI Timeout

I built a RKE cluster using cluster.yml file, then installed Rancher UI using helm3 in EC2 custom install Linux. In addition, I have created AWS LB (Target group for all 3 nodes). However, I am getting different types of time out errors once I access the Rancher UI in Firefox or Google Chrome. Is it a RKE cluster build issues or Rancher UI install issue? If any of you have a proper configuration, documents or sample cluster.yml, please share it with me. Thank you, I appreciate it.