Cluster IP: connection refused

Hi guys, I deployed kubernetes cluster with master and two nodes, and wordpress application as well for my Lab, all looks good. Then deployed Kasten10 for backup test, however Kasten10 is unable to detect applications in in kubernetes cluster. The Kasten10 support engineer has done debug, and advise it’s an issue with the kubernetes cluster network need to be narrowed down. Base on the debug log (shown below), it seems like Kasten10 is getting connection refused while trying to connect to the kubernetes ClusterIP: via 443, telnet from worker nodes the clusteIP (433) is all ok.

Does anyone know what should I do to fix that?
Thanks a lot for any suggestions